also synesthesia, "sensation in one part of the body produced by stimulus in another," 1881, in some cases via French, from Modern Latin, from Greek syn- "together" (see syn-) + aisthēsis "feeling" (from PIE root *au- "to perceive") + abstract noun ending -ia. Also psychologically, of the senses (colors that seem to the perceiver to having odor, etc.), from 1891. Related: Synaesthetic (adj.).