Where does “切歯” come from?

切歯 (Japanese) comes from Japanese 歯, from Middle Chinese 齒.

Ancestry of “切歯”, step by step

切歯 traces back through two separate lines of ancestry.

via Japanese

StepLanguageWordMeaning
1Japanesetooth; age
2Middle Chinese

via Japanese

StepLanguageWordMeaning
1Japanesecut, sever; cutting; to cut
Every word from Middle Chinese Every word from Japanese
切歯 — Etymology, Origin & Word History | Etymology Explorer