Where does “trine” come from?

trine (Middle English) comes from Middle French trin, from Latin trīnus, from Latin trēs, from Proto-Italic trēs, from Proto-Indo-European *tréyes.

Ancestry of “trine”, step by step

Step	Language	Word	Meaning
1	Middle French	trin	—
2	Latin	trīnus	—
3	Latin	trēs	—
4	Proto-Italic	trēs	three
5	Proto-Indo-European	*tréyes	—