exorcism (n.)

early 15c., "a calling up or driving out of evil spirits," from Late Latin exorcismus, from Greek exorkismos "administration of an oath," in Ecclesiastical Greek, "exorcism," from exorkizein "exorcise, bind by oath," from ex "out of" (see ex-) + horkizein "cause to swear," from horkos "oath," which is of uncertain origin. Some linguists propose a connection with herkos "fence," "in which case it would properly denote the oath as the bounds that one assumes, a restriction, tie, or obligation" or "a magical power that fences in the swearer" [Beekes], but this is not accepted by all. Earlier in the same sense was exorcization (late 14c.).