Where does “calumniosus” come from?

calumniosus (Latin) comes from Latin calumnia, from Proto-Italic kalwomniā, from Proto-Italic kalwomnos — deceiving, accusing.

Ancestry of “calumniosus”, step by step

Step	Language	Word	Meaning
1	Latin	calumnia	A cunning device, trickery, artifice, sophistry,...
2	Proto-Italic	kalwomniā	—
3	Proto-Italic	kalwomnos	deceiving, accusing

calumniosus — Etymology, Origin & Word History | Etymology Explorer