Where does “壬申” come from?

壬申 (Japanese) comes from Japanese 壬, from Japanese 兄, from Old Japanese あに, from Japanese の, from Old Japanese の, from Middle Chinese 能 — talent, ability.

壬申 (Japanese): Water Monkey, the ninth term of the sexagenary cycle

Definitions

Water Monkey, the ninth term of the sexagenary cycle

Ancestry of “壬申”, step by step

壬申 traces back through two separate lines of ancestry.

via Japanese 壬

Step	Language	Word	Meaning
1	Japanese	壬	the ninth of the ten heavenly stems; something I
2	Japanese	兄	elder brother; elder brother-in-law; Short for...
3	Old Japanese	あに	—
4	Japanese	の	genitive case marker; nominative case marker in a...
5	Old Japanese	の	plain, field
6	Middle Chinese	能	talent, ability

via Japanese 申

Step	Language	Word	Meaning
1	Japanese	申	the Monkey, the ninth of the twelve Earthly Branches
2	Japanese	猿	a monkey; Short for 日本猿; an ape
3	Chinese	猿	ape

Every word from Middle Chinese 能 →Every word from Old Japanese の →Every word from Japanese の →