anesthetic (adj.)
1846, "insensible;" 1847, "producing temporary loss of sensation," with -ic + Latinized form of Greek anaisthetos "insensate, without feeling; senseless, tactless, stupid" (see anesthesia). Noun meaning "agent that produces anesthesia" first used in modern sense 1848 by Scottish doctor James Young Simpson (1811-1870), pioneer in the surgical use of chloroform.