rankle, verb 1. (transitive or intransitive) To cause irritation, bitterness or acrimony. 2. (intransitive) To fester.

Etymology: From Middle English ranklen, ranclen, from Old French rancler, räoncler, draoncler (“to ulcerate, to form a boil”), from Old French draoncle (“a boil”), from Latin dracunculus (“little serpent”), diminutive of Latin dracō (“serpent, dragon”).

• rankle at Wiktionary