Where does “irrugō” come from?

irrugō (Latin) comes from Latin rūga, from Proto-Indo-European krewp-, from Proto-Indo-European krew- — to fall, collapse; scab; to fall, break, bruise.

Ancestry of “irrugō”, step by step

Step	Language	Word	Meaning
1	Latin	rūga	a crease in the face, wrinkle
2	Proto-Indo-European	krewp-	scab, crust; to become encrusted
3	Proto-Indo-European	krew-	to fall, collapse; scab; to fall, break, bruise

Words derived from “irrugō”

irrugatus
irrugate

Every word from Proto-Indo-European krew- →Every word from Proto-Indo-European krewp- →Every word from Latin rūga →