"cross, unstylish person," especially a woman or girl, 1817, from a group of related words of uncertain origin: Frump (n.) "a mocking speech" (1550s), "a sneer or snort" (1580s); frump (v.) "to mock, flout, taunt" (1570s); frumps (n.) "ill-humor" (1660s); frumpish (adj.) "cross-tempered" (1640s); and compare frumpy.
