Where does “trinalis” come from?

trinalis (Latin) comes from Latin trīnus, from Latin trēs, from Proto-Italic trēs, from Proto-Indo-European *tréyes.

Ancestry of “trinalis”, step by step

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

trinalis — Etymology, Origin & Word History | Etymology Explorer