Douglas Harper's Etymology Dictionary
rip-rap
also riprap, "loose stone thrown down in water or soft ground as foundation," 1822, American English, perhaps connected with earlier nautical word rip-rap meaning "stretch of rippling water" (often caused by underwater elevations), 1660s, probably of imitative origin (compare riprap "a sharp blow," 1570s).
Usage examples of "rip-rap".
He told me the longer riffs derived from classic sizz, while the backbeat was pure Transkei rip-rap.