Where does “rorandus” come from?

rorandus (Latin) comes from Latin roro, from Latin -ō, from Proto-Indo-European -ō — Derives nouns from roots.

Definitions

Step	Language	Word	Meaning
1	Latin	roro	I cause dew, drip; am moist; I drop, trickle,...
2	Latin	-ō	—
3	Proto-Indo-European	-ō	Derives nouns from roots

rorandus — Etymology, Origin & Word History | Etymology Explorer