Webster's Revised Unabridged Dictionary · 1913

Rancor

Rancor (ran"kẽr) , noun

[Old English rancour, Old French rancor, rancur, French rancune, from Latin rancor rancidity, rankness; tropically, an old grudge, rancor, from rancere to be rank or rancid.]

The deepest malignity or spite; deep-seated enmity or malice; inveterate hatred.
To stint rancour and dissencioun. — Chaucer
It would not be easy to conceive the passion, rancor, and malice of their tongues and hearts. — Burke
Rancor will out; proud prelate, in thy face I see thy fury. — Shakespeare
Rancor is that degree of malice which preys upon the possessor. — Cogan