Where does “trīnālis” come from?

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

Ancestry of “trīnālis”, step by step

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