Where does “-atus” come from?

-atus (Latin) comes from Proto-Italic -ātos, from Proto-Indo-European -éh₂tos.

Ancestry of “-atus”, step by step

Step	Language	Word	Meaning
1	Proto-Italic	-ātos	—
2	Proto-Indo-European	-éh₂tos	—

-atus — Etymology, Origin & Word History | Etymology Explorer