mid-14c., "incurable (of diseases, venom, etc.); extravagant (of expense); implacable (of hearts)," from Old French incorrigible "perfect, beyond rebuke or discipline" (14c.) or directly from Latin incorrigibilis "not to be corrected," from in- "not, opposite of" (see in- (1)) + corrigibilis, from corrigere "to correct," from com-, intensive prefix (see com-), + regere "to lead straight, rule" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule"). From mid-15c. as "incapable of improvement" (of persons). Related: Incorrigibly. As a noun, from 1746.