oxymoron (n.)

1650s, from Greek oxymoron, noun use of neuter of oxymoros (adj.) "pointedly foolish," from oxys "sharp, pointed" (from PIE root *ak- "be sharp, rise (out) to a point, pierce") + moros "stupid" (see moron). Rhetorical figure by which contradictory terms are conjoined so as to give point to the statement or expression; the word itself is an illustration of the thing. Now often used loosely to mean "contradiction in terms." Related: Oxymoronic.