Where does “さい” come from?

さい (Middle Chinese) comes from Japanese 左様, from Japanese 様, from Middle Chinese 樣.

Ancestry of “さい”, step by step

StepLanguageWordMeaning
1Japanese左様like that
2Japanese様way, style, appearance; be like, look like, seem...
3Middle Chinese樣—

Words derived from “さい”

Every word from Middle Chinese 樣 →Every word from Japanese 様 →Every word from Japanese 左様 →