"a pithy saying," 1550s, from Gk. apophthegma "terse, pointed saying," lit. "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.