JOHANNA MAYER: When I was a kid, we had this funny little tradition with our family car. We made sure that at all times there was a piece of wood inside the vehicle, like an actual stick, that we just picked up off the ground and kept in the cup holder.

 

That stick was for luck. We're running late but traffic looks good, knock on wood. Looks like we might get there right on time, knock on wood. We were running late a lot. And we would actually pick up the stick from the cup holder and give it a little knock.

 

I have always wondered where this phrase came from, but never bothered to figure it out until we got a note from a listener asking us about it. So today the origin of knock on wood and some of the psychology behind superstitious behaviors like keeping a stick in your car. Plus the answer to another listener question, where does the word tsunami come from?

 

I'm Johanna Mayer and this is Diction Dash, where I try and usually fail to guess the true meaning or origin of a word.

 

Kevin McLean is a freelance producer based in Davis, California. Hey, Kevin.

 

KEVIN MCLEAN: Hey, how's it going?

 

JOHANNA MAYER: I can hardly wait to hear where this phrase that I've used three million times comes from.

 

KEVIN MCLEAN: Yeah, yeah. Well, it is a very common superstition. According to the Oxford English Dictionary, knock on wood means to knock on something made of wood, as you said, as a superstitious act to ward off misfortune or bad luck. And actually, in the UK they say touch wood. Have you heard that before?

 

JOHANNA MAYER: I have heard that, yeah. And I think in Spanish, they say "toco madera," which means touch wood.

 

KEVIN MCLEAN: Yeah, so I mean, it is a super common superstition spanning many cultures and languages. And actually while I was looking it up, I kind of dove into some of the psychology literature behind superstitious behavior.

 

JOHANNA MAYER: Oh, I will definitely ask you more about that in a second. But first I have to know, do you have any superstitions, Kevin?

 

KEVIN MCLEAN: I don't think I have anything that is particularly superstitious, though I am sort of a creature of habit. So it's like when I do things that are different, I notice.

 

JOHANNA MAYER: I always knock on airplane doors before boarding.

 

KEVIN MCLEAN: Oh, interesting.

 

JOHANNA MAYER: I can't stop myself from doing it.

 

KEVIN MCLEAN: On the actual door or the door frame when you're walking in?

 

JOHANNA MAYER: The door frame as I'm walking into the airplane, just give it a little good luck knock. That's my superstition.

 

KEVIN MCLEAN: Wow, I did not find that in the knock on wood literature.

 

JOHANNA MAYER: There's no knock on the airplane?

 

KEVIN MCLEAN: Yeah.

 

JOHANNA MAYER: OK, I'm sorry. I derailed us.

 

KEVIN MCLEAN: No, no worries.

 

JOHANNA MAYER: You can go on.

 

KEVIN MCLEAN: Yeah, so it turns out there are a lot of different theories dating to a lot of different eras and not a ton of consensus on what is the earliest verifiable origin. So I'm actually going to present some of these theories to you. And we're going to do this two truths and a lie style. So you'll have to guess the one that's made up.

 

JOHANNA MAYER: I can't wait.

 

KEVIN MCLEAN: OK, so option number one. A British folklorist named Steve Roud traces the origins back to a 19th century children's game called "tiggy tiggy touch wood."

 

JOHANNA MAYER: OK.

 

KEVIN MCLEAN: It is-- yeah. Yeah, it's like tag where you're safe when you touch anything wood. So it's possible the reference could have been there before the game, but Roud sort of thinks that the game was the start. And for some reason the switch to knocking happened somewhere in North America, but there isn't really any clear information about the timing or reason for that.

 

JOHANNA MAYER: OK, if that's not the real answer, then that's an incredibly clever lie that you devised.

 

KEVIN MCLEAN: Oh, just you wait.

 

JOHANNA MAYER: Let's hear the other options.

 

KEVIN MCLEAN: All right, so option number two traces back to ancient paganism in Europe. Trees like oak, ash, hazel, and hawthorn were all of particular value and were believed to have protective or medicinal properties. So knocking on wood was a way to call on the protection of spirits that lived in the trees.

 

And actually the practice was eventually adopted into Christian traditions. So the wood alluded to Christ on a wooden cross and it was also symbolized by touching a crucifix or wooden rosary beads.

 

JOHANNA MAYER: Whoa.

 

KEVIN MCLEAN: Also complex.

 

JOHANNA MAYER: Yes. Yes, also incredibly detailed. OK, what's the last choice?

 

KEVIN MCLEAN: Yeah, option 3 is-- it's referenced in a 17th century description of sap harvest. A small mallet was used to knock on a tree trunk to listen for signs of beetle infestations. The Society of American Foresters says that the phrase is often attributed to sap harvest from sugar maple trees, but it actually originates from harvest from birch trees.

 

They also noted that it's not a very effective way of determining sap flow, so that might be where the association with just pure luck came into play.

 

JOHANNA MAYER: I'm just like sitting here in my closet with my mouth gaping open marveling at the detail of these lies. OK, so a quick recap. So option A is tiggy tiggy touch wood, the children's game where you're safe when you touch the wood.

 

Option B is the idea that certain woods were infused with special powers that you could call upon.

 

KEVIN MCLEAN: Yep.

 

JOHANNA MAYER: Right. OK, and option C is the beetles in trees. All right, so I'm just trying to identify the lie. OK, I think the lie is the beetles in the trees. C.

 

KEVIN MCLEAN: You are correct. That is the false one.

 

JOHANNA MAYER: Thank God. I never get this right.

 

KEVIN MCLEAN: Yeah, just to sort of recap, so tiggy tiggy touch wood is probably the most likely origin. That folklorist Steve Roud definitely feels like that is the most likely origin of it. And he feels the tracing back to paganism is "absolute nonsense," to quote him exactly. And yeah, the sap harvest was just a very tasty, tasty lie.

 

JOHANNA MAYER: Can you tell me a little bit about the psychology behind superstition and things like this?

 

KEVIN MCLEAN: Yeah, so I guess the short version is regardless of whether our behavior actually gives us good luck or keeps our mothers' backs from breaking, we do these things because of how they make us feel. So there's one possible, and I think pretty intuitive, explanation that it basically gives us a sense of control in situations where we don't have a lot of control.

 

My favorite study that I found was basically it was people that scored high on a desire for control scale were more likely to knock on a wooden table when asked questions about horrible things that might happen, like getting into a deadly car crash, particularly when they were under stress.

 

So there was a group that was asked all these horrible questions right before they were about to take an exam and then a group that was taken when there was no exam on the horizon. So the stressed people that were thinking about horrible situations were much more likely to be knocking on wood when they gave answers.

 

JOHANNA MAYER: Yeah, I guess every time I'm getting on a plane and knocking on the plane door, I'm thinking about a plane crash, a potential horrible situation.

 

KEVIN MCLEAN: Yeah, I mean, there's only so much you can control. But definitely if you don't not knock on the door of that plane, it is going to go down.

 

JOHANNA MAYER: Kevin McLain, thank you so much.

 

KEVIN MCLEAN: No problem. Thank you.

 

JOHANNA MAYER: And now we have Shalina Chatlani, a health care reporter for the Gulf States newsroom. Hey, Shalina.

 

SHALINA CHATLANI: Hey, Johanna. Really glad to be here.

 

JOHANNA MAYER: All right, so what listener suggested what are you going to be quizzing me about?

 

SHALINA CHATLANI: OK, I chose the word tsunami because I think they're super fascinating. And I started to think about that really beautiful and famous piece of artwork. I don't know if you know it. It looks like a Japanese woodblock print of a big, blue wave with frosty white curls.

 

JOHANNA MAYER: I had a poster of that in my college dorm room.

 

SHALINA CHATLANI: Yes, like in every college kids dorm room.

 

JOHANNA MAYER: Yeah.

 

SHALINA CHATLANI: So this piece is called the Great Wave of Kanagawa by Katsushika Hokusai. And this artwork, Mount Fuji, the tallest mountain in Japan, is dwarfed by a gigantic wave just waiting to be crashed down on.

 

So tsunami is a Japanese word, but what do you think it means? Here are your choices. A, tidal wave; B, harbor wave; C, the dragon's wave; D, seismic sea waves; or E, wave of doom.

 

JOHANNA MAYER: Man, I should say I actually lived in Japan for a couple of years and used to speak a little bit of Japanese, but I have no clue as usual. I'm going to go with wave of doom.

 

SHALINA CHATLANI: I'm glad you chose that, but you're wrong.

 

JOHANNA MAYER: I'm usually wrong. OK, wait. Can I get a second guess?

 

SHALINA CHATLANI: Yeah, go for it.

 

JOHANNA MAYER: OK, then I'm going to try-- I'm going to try dragon wave.

 

SHALINA CHATLANI: No, I'm sorry.

 

JOHANNA MAYER: Ah.

 

SHALINA CHATLANI: Those were my fun ones to trip you up.

 

JOHANNA MAYER: Let's just keep going down the list. I'm going to say harbor wave.

 

SHALINA CHATLANI: OK, you got it this time.

 

JOHANNA MAYER: OK, third time's the charm.

 

SHALINA CHATLANI: So it stands for harbor wave because "tsu" means harbor and "nami" means wave. So that makes sense, right? Tsunamis are a series of long waves that are caused by a sudden displacement of the ocean. And these waves rush to the shore and can be hundreds of feet tall and travel very fast.

 

But of course, water moves around for a lot of reasons. So what do you think causes tsunamis? Here are your choices. A, asteroids; B, earthquakes; C, volcanoes; or D, all of the above.

 

JOHANNA MAYER: I was very certain that it was earthquakes, but then you threw in that all of the above. And you know what? I'm not falling for your bait. I'm going to say earthquakes.

 

SHALINA CHATLANI: I'm sorry to say, but you fell right into my trap. So since 1900, around 80% of recorded tsunamis have been caused by earthquakes typically below or near the ocean floor. So that's when the Earth's tectonic plates move around and crash into each other, causing those big movements of water.

 

But underwater volcanic eruptions, landslides, possibly asteroids, and even some types of weather events, though rare, can cause them.

 

JOHANNA MAYER: Landslides can cause tsunamis?

 

KEVIN MCLEAN: Yeah.

 

JOHANNA MAYER: And asteroids?

 

SHALINA CHATLANI: Mm-hmm.

 

JOHANNA MAYER: Has that-- so that's happened in the past? Like an asteroid is just slammed down into the ocean and caused a tsunami?

 

SHALINA CHATLANI: Well, there is at least one very famous event. The asteroid that is thought to have killed all of the dinosaurs.

 

JOHANNA MAYER: Oh.

 

SHALINA CHATLANI: When it crashed into the Earth, it's thought to have created a tsunami so massive it would have made waves around the globe.

 

JOHANNA MAYER: That is a big wave. OK, so to recap. Tsunamis can be caused by many different things, though usually earthquakes. And the word tsunami means harbor wave.

 

SHALINA CHATLANI: Yes, that's exactly right. And it might have been something Japanese fisher people came up with. We first see it in print in 1611, so it's at least several centuries old. So the word makes it into English by the 19th century.

 

In 1896, the northeast coast of Hondo in Japan-- that's the historic name for the main island that today we call Honshu-- it was struck with a huge tsunami, the biggest of that century. And it killed nearly 27,000 people.

 

An American journalist reported on it for the National Geographic. So that's when it's believed to have shown up for the first time in the English language, about 3 centuries after it was used in Japanese writing.

 

JOHANNA MAYER: And the Japanese word just stayed intact, . I guess

 

SHALINA CHATLANI: Yeah, it sort of makes sense that we're ending up using the Japanese word because a lot of the larger tsunamis in history have happened in Japan.

 

JOHANNA MAYER: Yeah.

 

SHALINA CHATLANI: That's likely because Japan is located along what's known as the Ring of Fire. It's the most active earthquake belt in the world. It's also home to much of the world's volcanoes. So this is where several of the Earth's tectonic plates meet and often crash into each other.

 

But today of course, volcano and earthquakes aside, we use the word tsunami in a variety of ways and pretty regularly.

 

JOHANNA MAYER: Shalina Chatlani, thank you so much.

 

SHALINA CHATLANI: Thanks for having me.

 

JOHANNA MAYER: That's it for this round of Diction Dash. If you have a word you've always wondered about, send us an email at podcasts@sciencefriday.com or call us up and leave a voicemail. We might play your question on the show. The number is 929-499-WORD. That's 929-499-9673. Please keep sending us your suggestions and we'll keep making these episodes.

 

This episode of Science Diction was produced by me, Johanna Mayer.

 

ELAH FEDER: And me, Elah Feder.

 

DANIEL PETER SCHMIDT: And me, Daniel Peter Schmidt.

 

JOHANNA MAYER: Daniel's also our composer, and they mastered this episode. We had fact-checking help from Robin Palmer. Nadja Oertelt is our chief content officer. And she's a great boss, totally supportive, takes care of business.

 

The one thing is our communication styles are little different. Something's off. Sometimes it just feels like we're not even speaking the same language.

 

KEVIN MCLEAN: Tiggy tiggy touch wood.

 

JOHANNA MAYER: Piggy piggy touch wood?

 

KEVIN MCLEAN: Tiggy tiggy touch wood.

 

JOHANNA MAYER: Kitty kitty touch wood?

 

KEVIN MCLEAN: Ah, tiggy.

 

JOHANNA MAYER: See you soon.