Where does “pineus” come from?

pineus (Latin) comes from Latin -eus, from Proto-Italic *-eos.

Ancestry of “pineus”, step by step

Step	Language	Word	Meaning
1	Latin	-eus	argentum + API → argenteus; ferrum + API →...
2	Proto-Italic	*-eos	—

pineus — Etymology, Origin & Word History | Etymology Explorer