慈姑

Concerning the name of the plant, Compendium of Materia Medica says:

一根歲生十二子，如慈姑之乳諸子，故以名之。 [Classical Chinese, trad.][▼ expand/hide]

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一根岁生十二子，如慈姑之乳诸子，故以名之。 [Classical Chinese, simp.]

Yī gēn suì shēng shí'èr zǐ, rú cígū zhī rǔ zhū zǐ, gù yǐ míng zhī. [Pinyin]

One [arrowroot] yields twelve fruits, as a kind mother gives birth to many sons, hence it is so called.

慈姑

1. (literary) husband's mother; mother-in-law
2. arrowhead (Sagittaria sagittifolia)

Unknown. One theory suggests that this is an alteration from 川芋 (kawa imo, “river tuber”), but the old kana spelling of くわゐ (kuwawi) for 慈姑 does not match the old kana spelling of かはうも (kafaumo) for 川芋. This is more likely a compound of 鍬 (kuwa, “plow”), from the shape of the leaves, plus an unknown element ゐ (wi).

The kanji are ateji, borrowed from the Chinese name for this plant.

• (Irregular reading)
  • (Tokyo) くわい [kùwáí] (Heiban – [0])[1][2]
  • IPA^(key): [kɯ̟ᵝɰᵝa̠i]

慈姑 (hiragana くわい, katakana クワイ, rōmaji kuwai, historical hiragana くわゐ)

1. (botany) the arrowhead plant, Sagittaria trifolia var. edulis, cultivated since ancient times for its edible bulb

As with many terms that name organisms, this term is often spelled in katakana, especially in biological contexts, as クワイ.