"pithy saying," 1550s, from Greek apophthegma "terse, pointed saying," literally "something clearly spoken," from apophthengesthai "to speak one's opinion plainly," from apo- "from" (see apo-) + phthengesthai "to utter." See aphorism for nuances of usage. Spelling apophthegm, restored by Johnson, is preferred in England, according to OED.