"full of rancor, implacably spiteful," 1580s, from rancor + -ous. Related: Rancorously; rancorousness.
Entries linking to rancorous
rancor n.
c. 1200, rancour, "a nourished envy; bitterness, hatred, malice," from Old French rancor "bitterness, resentment; grief, affliction," from Late Latin rancorem (nominative rancor) "rancidness, a stinking smell" (Palladius); "grudge, bitterness" (Hieronymus and in Late Latin), from Latin rancere "to stink," a word of unknown etymology (compare rancid). Sometimes in 15c. medical works the word is used in English in its literal Latin sense.
-ous
word-forming element making adjectives from nouns, meaning "having, full of, having to do with, doing, inclined to," from Old French -ous, -eux, from Latin -osus (compare -ose (1)). In chemistry, "having a lower valence than forms expressed in -ic."