Where does “四” come from?

四 (Japanese) comes from Middle Chinese 四, from Proto-Sino-Tibetan *pV-lij.

四 (Japanese): four, 4; the fourth

Definitions

Step	Language	Word	Meaning
1	Middle Chinese	四	—
2	Proto-Sino-Tibetan	*pV-lij	—

四 — Etymology, Origin & Word History | Etymology Explorer