rive v.

"of or pertaining to river banks, situated on or near a river bank," 1849, with -an + Latin riparius "of a river bank," from riparia "shore," later used in reference to the stream flowing between the banks, from ripa "(steep) bank of a river, shore."

This is probably etymologically "break" (and indicating the drop off from ground level to the stream bed), or else "that which is cut out by the river," from PIE root *rei- "to scratch, tear, cut" (source also of Greek ereipia "ruins," eripne "slope, precipice;" Old Norse rifa "break, to tear apart;" Danish rift "breach," Middle High German rif "riverbank, seashore;" English riven, rift).

Riparious, of animals, "living on or in river banks," is from 1650s.

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."