1553, 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.