It was Oakland rapper Keak Da Sneak who claims to have invented the term: upon being told by his mother that he was “hyperactive”, Keak repeated the term as “hyphy”. Since then, hyphy has come to refer to a complex group of cultural activities synonymous with Oakland: it is at once a sound, a behavior, a choice in recreational drugs.
2009, Mickey Hess, editor, Hip Hop in America: A Regional Guide, volume 1, ABC-CLIO, page 281