"horizontal section of sail rolled or folded" to reduce the area exposed to the wind, late 14c., rif (mid-14c. in rif-rope "rope used in tying down a reef"), from a Scandinavian source such as Old Norse rif "reef of a sail," probably a transferred use of rif "ridge under the sea; rib" (see rib (n.) and compare reef (n.1)). German reff, Swedish ref, Norwegian riv, Danish reb likely all are from the Old Norse word.

"low, narrow rock ridge underwater," 1580s, riffe, probably via Dutch riffe, from a Scandinavian source such as Old Norse rif "ridge in the sea; reef in a sail," literally "rib" (see rib (n.)). Also extended to the low islands formed by coral debris or to any extensive elevation of the bottom of the sea.

also ribband, in ship-building, "long, flexible timber extending the length of the vessel body and nailed or bolted around the ribs to hold them in position," 1711, from rib (n.) + band (n.1).

1776, originally of land, "having rocky rib-like ridges;" figurative sense of "resolute" is recorded by 1887; see rock (n.) + rib (n.).