A kappa's name literally means "river child." A tengu's name began as a word for a meteor.
Sorted by how they actually got their names, twelve yokai fall into three clear groups.
Named for Exactly What They Look Like or Do
01
Kappa (河童) — "River Child"
The name is thought to come from "kawa-warawa," meaning "river child," later slurred into "kappa." This water-dwelling creature is said to draw its strength from water held in a dish-shaped hollow on its head — a detail that lines up neatly with its "child of the river" name.
02
Zashiki-Warashi (座敷童子) — "Reception-Room Child"
The name is almost literal: "zashiki" is a formal tatami reception room in an old-style house, and "warashi" is a Tohoku dialect word for "child." A household said to host this child spirit was believed to prosper, while one it left behind was said to decline.
03
Tamamo-no-Mae (玉藻前) — "Jeweled Seaweed"
A beautiful court lady serving Emperor Toba is said to have earned this name after her body glowed like a jewel one night when the palace lights went out. Later retellings revealed her true identity: a thousand-year-old nine-tailed fox.
04
Okuri-inu (送り犬) — "Escorting Dog"
A dog-like spirit said to trail travelers on mountain roads at night, its name means exactly what it sounds like: an "escorting dog." Trip and fall, and it's said to attack — but pretend to rest and thank it politely, and it will see you safely home instead.
05
Akaname (垢なめ) — "Grime Licker"
Its name simply describes what it does: "aka" means grime, and "nameru" means to lick. It's said to appear in neglected, unwashed bathrooms to lick up the built-up filth — a fittingly literal warning against letting dirt pile up.
06
Tofu Kozo (豆腐小僧) — "Tofu Boy"
True to its name, this yokai is a small boy ("kozo") who wanders around carrying a tray of tofu. It first appeared in mid-Edo-period illustrated storybooks and, unlike most yokai, was almost entirely harmless — a mascot-like figure people found endearing rather than frightening.
07
Ittan-momen (一反木綿) — "A Bolt of Cotton"
This Kagoshima yokai looks like a long strip of white cloth. "Ittan" is a traditional unit for a bolt of cotton cloth, roughly 10 meters, and "momen" means cotton — a name that describes its shape exactly, as it flutters through the dusk air and wraps around unlucky travelers.
Named for a Sound, a Cry, or a Borrowed Word
08
Tengu (天狗) — "Heavenly Dog"
The word arrived from China during the Nara period as "tiangou," literally "heavenly dog." It originally described a meteor streaking across the sky with a thunderous roar, its blazing tail likened to a dog racing through the heavens. The familiar red-faced, long-nosed mountain spirit came much later — the name predates the creature it now describes.
09
Nue (鵺)
This chimera, famously hunted down in The Tale of the Heike, takes its name from an eerie bird called the "nue-dori" — today's scaly thrush — whose cry it was said to share. The monster was apparently named for its voice before anyone described the rest of it: a monkey's head, a raccoon dog's body, a snake's tail.
Source: The Tale of the Heike
10
Rokurokubi (ろくろ首)
"Rokuro" refers to the pulley mechanism used to raise a bucket from a well by winding a rope. Just as pulling the rope makes the bucket shoot upward, this creature's neck was imagined to stretch and retract the same way — the likely origin of its name.
Named — But Nobody Agrees Exactly Why
11
Shuten-doji (酒呑童子)
The oni chieftain said to terrorize Mount Oe earned his name — literally "sake-drinking boy" — from his love of drink, according to the classic Oeyama Ekotoba scroll. Another theory traces it to "sute-doji," meaning "abandoned child," reflecting legends that he was orphaned young. Both explanations are still cited, with no consensus on which came first.
Source: Oeyama Ekotoba scroll
12
Nurarihyon (ぬらりひょん / 滑瓢)
One leading theory splits the name into two old words: "nurari," meaning slippery or elusive, and "hyon," meaning unexpected or strange. Its kanji spelling, 滑瓢 — "slippery" plus "gourd" — echoes the same idea: a creature that's impossible to pin down. No single account is confirmed as the original.