Where does “騎馬戦” come from?

騎馬戦 (Japanese) comes from Japanese 戦, from Middle Chinese 戰.

騎馬戦 (Japanese): A kind of chicken fight: a Japanese game, in...

Definitions

Step	Language	Word	Meaning
1	Japanese	戦	a battle, conflict, fight, war; a game, match; a...
2	Middle Chinese	戰	—

騎馬戦 — Etymology, Origin & Word History | Etymology Explorer