Where does “Placidus” come from?

Placidus (Latin) comes from Latin -idus, from Proto-Italic *-iðos.

Ancestry of “Placidus”, step by step

Step	Language	Word	Meaning
1	Latin	-idus	tending to
2	Proto-Italic	*-iðos	—

Placidus — Etymology, Origin & Word History | Etymology Explorer