Stop me if you’ve heard this one. Two men aged around 50 enter a sushi restaurant. One orders a raincoat, the other a garage. What looks like the beginning of a “Monty Python” sketch is in fact the stuff of a most typical oyaji gyagu (おやじギャグ), or old man’s joke/gag. Such jokes normally center around words with similar or identical reading, but with an entirely different meaning. Linguists call these homophones.

In the above case, the joke derives from an intended misreading of the words kappa and shako. While kappa in the context of a sushi restaurant is usually interpreted as an abbreviated form of kappa maki (かっぱ巻き, a cucumber sushi roll), kappa when spelled differently (合羽) means raincoat. This is also available as an English loanword, レインコート, which is what one of the guys used when making his order. As for the other one, his joke was based on the fact that shako (蝦蛄) is not only a type of shrimp, but also a dry place to leave your kuruma (car) (車庫), which in Japanese is equally known by the katakana word ガレージ, garage.

One common feature of the oyaji gyagu is that those homophones frequently occur in a single, more or less meaningful, phrase. Here are a few well-known examples of this type:

• Sukī ga suki (スキーが好き, I like skiing)

• Shio ga nai no wa shō ga nai (塩がないのはしょうがない, It can’t be helped if there is no salt)

• Kono ikura wa ikura? (このイクラはいくら?, How much is this salmon roe?)

• Kon ya kū no wa konnyaku (今夜食うのは蒟蒻, “I’ll eat konnyaku [devil’s tongue jelly] this evening.”)

If you don’t think that’s funny, don’t worry. Here is a paraphrase of what the Japanese Wikipedia site states about this type of joke: The oyaji gyagu is simple and easy to understand. The cheaper it is, the more it poses a dilemma to the hearer, who may perfectly get the joke, but just won’t be able to laugh about it. More than entertaining the hearer of such jokes, it seems that the pleasure is with the teller. Nevertheless the latter normally expects some laughter from the former.

Although in a larger humor survey conducted by the Asahi Shimbun in 2005, only 18 percent of respondents openly admitted they disliked oyaji gyagu, the most frequent types of reaction, in my experience as a hearer and occasional teller (yes, I confess), are complaints about a sudden chill in the room (アッ寒い!, Ah, samui!), an interjection of disapproving disbelief (ハッ? Hah?), or a very uncomfortable silence (・・・).

Nevertheless, the oyaji gyagu is much better than its reputation. The idea of selling different meanings by the same sound value, which is basically what an oyagi gyagu is all about, has been of fundamental importance in the development of writing. For example, the Chinese character 来 was originally used to denote a certain type of wheat. That it is the standard character for “come” today is due to the simple coincidence that the two words happened to have the same pronunciation. As no character was available yet for the latter, some (Chinese) oyaji at some ancient point in history came up with the idea of using the wheat character for “come” as well, and the same thing soon happened with many other characters such as 足 (foot), which was later on also used for “to suffice,” or 万 (10,000), which derives from the character for scorpion. The technical term for this is “rebus principle,” but in effect it is nothing but a large-scale application of the oyaji gyagu, with unforeseeably great consequences for civilization.

Oyaji gyagu also play an important role in Japanese poetry, where they go by the name of kakekotoba (掛詞, pun). Though few people would necessarily want to connect these two things, it is a fact that kakekotoba work on exactly the same principle as a decent oyaji gyagu. Waka poets are famous for wordplays that exploit the ambiguity of terms like, say, kiku, which can mean both “listen” (聞く) and “chrysanthemum” (菊), or matsu, which depending on spelling is either “wait” (待つ) or “pine tree” (松). It’s a very thin line from the ridiculous to the sublime.

Back in the present, the oyaji gyagu principle has also found its way into product naming, as described by Mark Schreiber in this column last week, and into Netspeak. To give just one example of the latter: A recent catchphrase on discussion sites such as Mixi or 2channel is the somewhat enigmatic term imakita sangyō (今北産業), which literally translates as something like “now north industry.” The term is normally used by people who have just joined in (今来た, ima kita) a running discussion thread and want to get a brief, three-line (三行, san gyō) summary of what’s happened so far. Again, the thing that makes it all work is an oyaji gyagu homophony of the terms in question (plus, initially at least, a mistyped kanji by some user, oyaji or other).

What’s so funny about the oyaji gyagu, then? Nothing, maybe, but its importance for Japanese society and culture — both high and rather low — can hardly be overrated.