Is it farther or further?
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). As "a procedure for the prevention of pain in surgical operations," from 1846.
anesthetic an·es·thet·ic (ān'ĭs-thět'ĭk)
An agent that reversibly depresses neuronal function, producing total or partial loss of sensation. adj.
Characterized by the loss of sensation.
Capable of producing a loss of sensation.
Associated with or due to the state of anesthesia.