Where does “yakusa” come from?

yakusa (French) comes from Japanese やくざ, from Japanese 九, from Old Japanese 九.

Ancestry of “yakusa”, step by step

StepLanguageWordMeaning
1Japaneseやくざsomething that is worthless or useless; yakuza:...
2Japanese九nine; ninth; the ninth
3Old Japanese九—
Every word from Old Japanese 九 →Every word from Japanese 九 →Every word from Japanese やくざ →