Where does “三将” come from?

三将 (Japanese) comes from Japanese 三, from Middle Chinese さん.

三将 (Japanese): a "third", the third highest-ranking member of a sport team, generally the third strongest member of a team of four or more, or the weakest of a trio

Definitions

a "third", the third highest-ranking member of a sport team, generally the third strongest member of a team of four or more, or the weakest of a trio

Ancestry of “三将”, step by step

三将 traces back through two separate lines of ancestry.

via Japanese 三

Step	Language	Word	Meaning
1	Japanese	三	three, 3; third; three
2	Middle Chinese	さん	—

via Japanese 将

Step	Language	Word	Meaning
1	Japanese	将	a commander; a general, admiral, or other...
2	Middle Chinese	將	—

Every word from Middle Chinese さん →Every word from Japanese 三 →