anesthesia (n.) Look up anesthesia at Dictionary.com
1721, "loss of feeling," Modern Latin, from Greek anaisthesia "want of feeling, lack of sensation (to pleasure or pain)," from an- "without" (see an- (1)) + aisthesis "feeling," from PIE root *au- "to perceive" (see audience). With abstract noun ending -ia. As "a procedure for the prevention of pain in surgical operations," from 1846. Aesthesia "capacity for feeling" is attested in English from 1879, perhaps a back-formation.