Where does “東男” come from?

東男 (Japanese) comes from Japanese 東, from Old Japanese 東, from Old Japanese 天, from Proto-Japonic *amay.

東男 (Japanese): a man from eastern Japan (historically, particularly Edo) where men are often thought of as manlier

Definitions

a man from eastern Japan (historically, particularly Edo) where men are often thought of as manlier

東男 traces back through two separate lines of ancestry.

Step	Language	Word	Meaning
1	Japanese	東	the east; the Orient; an easterly
2	Old Japanese	東	the east; the lands east of the 都
3	Old Japanese	天	sky, heavens
4	Proto-Japonic	*amay	—

Step	Language	Word	Meaning
1	Japanese	男	a man; a male; a male lover
2	Middle Chinese	男	—