O.E. hwisprian "speak very softly" (only in a Northumbrian gloss for L. murmurare), from P.Gmc. *khwis- (cf. M.Du. wispelen, O.H.G. hwispalon, Ger. wispeln, wispern, O.N. hviskra "to whisper"), imitative and probably related to O.E. hwistlian "to whistle." The noun is from 1596.