What's going on
Japan has a long tradition of zokushin — folk beliefs and taboos passed down through generations, often tied to specific regions. Some of these, like "don't whistle at night or snakes will come," have plausible-ish explanations (whistling disturbed people's sleep in old houses, snakes are attracted to certain sounds). But a popular idea floating around is that all folk superstitions must have some kind of scientific or practical basis. This thread pushes back on that.
A user posted the original observation that while it's a fun, catchy idea that folk taboos always have logical roots, the reality is that a lot of them are just... completely inexplicable. Their examples: "If your butt itches, you'll get a good sardine catch" (recorded in Iwate, Akita, Ishikawa, and Nagano prefectures) and "Don't lend money to someone with thick leg hair" (Iwate). The thread then became a collective dig through regional oddities — and an attempt to rationalize the ones that might actually make sense.
Comments
The idea that every folk taboo has a scientific explanation is catchy and fun — but that’s just not how it works. So let’s really lean into the weird, inexplicable ones. Like “if your butt itches, you’ll get a good sardine catch” (Iwate, Akita, Ishikawa, Nagano) or “don’t lend money to someone with thick leg hair” (Iwate). More of these, please.
俗信や禁忌には必ず科学的な理由があるというのはキャッチーで面白いのですがそんなんばっかじゃないので、やはり「尻の穴がかゆいとイワシが捕れる(岩手、秋田、石川、長野)」とか「すね毛の濃い人に金を貸すな(岩手)」とかそういうよくわかんない禁忌をドシドシ上げていくべきである。
I can’t believe there are actually folk sayings like that where people live…
そんなおもしろ言い伝えが地元にあったなんて……
The ones that clearly never traveled beyond one village are way more interesting than the ones that feel like they’ve absorbed some general wisdom along the way.
どこかでリテラシーを吸収したような伝承より、これ絶対お前の区画から出てないだろって伝承の方が面白いと思います
Never heard any of these… (Iwate resident)
一つも聞いたことがない……（岩手県民）
What is this, I’ve never heard of it… scary… (from Iwate)
何それ知らん……怖……(岩手出身)
What happened in Iwate?
岩手に何があったんだ
I’m from the Hei region of Iwate where if you said “my butt is itchy~” someone would chime in “big sardine haul!”, but I had no idea about the leg hair thing… wonder where exactly that one’s from. Iwate’s a big place after all.
お尻かゆい〜っていうと「鰯が大漁」って合の手がくる岩手閉伊地方出身だけど、すね毛は知らんかった…どこで言うのかな。岩手広いからな…
Nagano catches sardines…?
イワシがとれるながの……？
The fact that it’s said in landlocked Nagano is hilarious.
海の無い長野県でもいわれているのおもしろい。
When you think about it calmly, why is Nagano even in this? Nagano has nothing to do with sardines.
冷静に考えたらなんで長野やねんイワシ関係ないやろ長野
I don’t believe sardines are caught in Shinshu. (“Shinshu” is an old name for Nagano Prefecture, a mountainous inland region.) How on earth did this taboo originate there — the curiosity never ends ^_^
信州では鰯は捕れないと思うがどうか。いかにして信州でこの禁忌が生まれたか興味は尽きない^_^
Northern Nagano especially has really strong ties with Niigata and Toyama, so it’s plausible. (Even around Shiojiri in central Nagano they’ve been selling firefly squid for ages, and fishing shops in Matsumoto have surprisingly well-stocked saltwater fishing sections.)
長野県、特に北信は新潟＆富山との関わりがめっちゃ強いのであり得る。（中信…塩尻あたりでも昔からホタルイカ売ってたり、松本の釣り道具屋で海釣りコーナーが充実してたり）
I don’t think Akita actually catches many sardines these days. And with washlets so widespread now, (referring to the Japanese bidet toilet seat, now standard in most homes) there’s probably not as much itching going on either.
現在の秋田県はあまりイワシとれないイメージです。ウォッシュレット普及しすぎですね。
The butt-itching one seems like it could be explained as a weather prediction thing — like humidity or something.
尻の穴は湿度とかの天候予測系で説明できそう
It’d be interesting if the conditions under which pinworms aggressively lay eggs happened to overlap with the conditions that draw sardines close to shore.
蟯虫が積極的に産卵する条件とイワシの寄る条件が被ってるとかあれば面白いな
I always figured thick leg hair = not enough friction to thin it out = someone who doesn’t go outside much = no steady income.
脛毛が濃い人…は毛がモサモサするくらい摩擦がない＝外に出てない人（稼ぎがないor不安定）ってことなんかと思ってた
Maybe it’s: thick leg hair → high testosterone → builds muscle easily → if they don’t pay you back, you can’t physically take it from them…? lol
すね毛が濃い↓テストステロンが多い↓筋肉がつきやすい↓いざという時力ずくで回収できない…とかでしょうか？w
My father used to say “don’t lend money to someone with thick leg hair,” so I asked him why, and he said: people who work hard rub their legs enough to thin out the hair, so thick leg hair means someone who doesn’t work. Made sense and didn’t make sense at the same time. This was in Yamagata.
脛毛が濃い人に金を貸すな、と父が言っていたので何故と聞いたらがんがん働く人は足が擦れて脛毛が抜けるから。故に働かない人は脛毛が濃い、解るような解らないような答えでした。山形県です。
It’s a bit of a “does and doesn’t make sense” kind of story, but just knowing that a folk belief like that actually exists and that there are people who still say it — I’m genuinely moved. This is one of those moments that makes being online worth it. Thank you so much for sharing this 🙏
解るような解らないような話ではありますが、本当にそういう俗信が伝わっててそれを仰有る方が居られるのだな〜、というのがわかってとても感動しております、Twitterやってて良かった瞬間であります、お教え下さりありがとうございます🙏
My father was born in the early Showa era. (Early Showa refers to the 1920s–30s, a generation that grew up before and during World War II.)
昭和一桁の父でした。
Come to think of it, both my husband and my brother are the reliable type, and both have thin leg hair.
確かに、夫も兄貴も信用できるタイプで、ともに脛毛が薄い。
Guess no one’s lending me money then.
金貸してもらえねぇな
“Itchy butt → good sardine catch”: high humidity causes stuffiness → plankton bloom → conditions that bring sardines close to shore → overlaps with fishing season. “Don’t lend to thick leg hair”: thick hair = high testosterone = impulsive = bad at repaying. Also: in old times, people who worked hard wore down their leg hair, so thick hair = lazy.
「尻の穴がかゆいとイワシが捕れる」・高湿度でムレやすい時期＝プランクトンが増えイワシが岸に寄りやすい気象条件で漁期と重なる。「すね毛の濃い人に金を貸すな」・すね毛濃い＝テストステロン高め、衝動性強めで返済ルーズ。・昔は働く人は足酷使で毛が減るから濃い＝怠け者
When there are lots of stink bugs, some say “big snowfall coming” and others say “it’ll be a light snow year” — so “they’re not related” is probably the correct answer.
カメムシが多いと「大雪だ」と「雪が少ない」が両方おるから「関係ない」が正解だど思ってる。
Around where I live there’s one that says “if your ear itches, money is coming your way.” Is that like… compensation for the discomfort of having an itchy ear?
うちのあたりには「耳が痒いとお金が入ってくる」というのがある 耳が痒いという不快の対価なのか
Well, I think it’s a kind of statistics in a loose sense — like how we lump all kinds of unidentified respiratory illnesses together and call them “colds.” Anyway, it sounds like I won’t be getting any loans in Iwate…
まあ、ある種の統計ではあると思う よくある感冒で原因の特定されていないものを風邪と呼ぶ雑な感じで ただ、私は岩手では金は借りられないらしい…
Never mind folk taboos — even in biological evolution, things don’t always have a neat scientific reason behind them.
「俗信や禁忌には必ず科学的な理由がある」どころか、例えば生物の進化についても必ずしも科学的な理由があるとは限らないのですよね。
There’s a real chance that some of these started out as the ancient equivalent of a nonsense internet meme, and somehow ended up being passed down as serious folk wisdom.
今で言う意味不明なネットミームみたいなノリがいつの間にか禁忌みたいに語られてる可能性ありそう。
My take
The fact that it got passed down at all suggests it must have hit home often enough. Though the hit rate was probably pretty low.
Source & translation note
Comments loosely translated for tone. Reactions collected from Togetter and X threads.
View original thread →