riff [M20th] The musical riff, a short repeated musical phrase, is probably simply a shortening and respelling of refrain, a repeated phrase, especially one breaking up the verses in a song. Refrain is recorded in Late Middle English but is a rare word before the 19th century. It comes from French refrain. This most probably comes from an unrecorded post-classical variant, refrangere, of classical Latin refringere, source of refract [M16th], formed from frangere ‘to break’ (see fraction).