also: もっしょくし
noun
gallnut; oak gall; nutgall
A growth on oak trees caused by insect larvae, historically used for making ink and tannin. Technical term in botany and historical contexts.
没食子は、昔、インクの原料として使われた。
Gallnuts were used as a material for ink in the past.
この標本には没食子がいくつか付い
This specimen has several oak galls attached.
虫こぶ is a general term for any plant gall caused by insects, while 没食子 specifically refers to oak galls used for ink or tannin.
The kanji 没食子 literally means 'lost-food child', but the exact derivation is uncertain. It is a traditional term for oak galls, likely adopted from Chinese medical or technical texts.