early 14c., "a split, a breaking, an act of tearing or rending," from a Scandinavian source (compare Danish and Norwegian rift "a cleft," Old Icelandic ript (pronounced "rift") "breach;" related to Old Norse ripa, rifa "to tear apart, break a contract" (see riven). Probably influenced in Middle English by rive (v.).
From late 14c. as "a cleft, fissure, or chasm in the earth;" by c. 1400 as "a crack, split, or similar opening" in anything. Figurative use from 1620s. Specific modern geological sense of "large fault running parallel to the relief" is by 1921. As a verb, c. 1300, "to split, form fissures, gape open."