riffle v.

1754, "to make choppy water," American English, perhaps a variant of ruffle "make rough." The word meaning "shuffle" (cards) is recorded by 1894, perhaps echoic; hence "skim, leaf through quickly" (of papers, etc.), by 1922. The noun meaning "rapid formed by a rocky obstruction in the bed of a river" is by 1785. Related: Riffled; riffling.