late 13c., "be a sign of, indicate, mean," from Old French signifier (12c.), from Latin significare "to make signs, show by signs, point out, express; mean, signify; foreshadow, portend," from significus (adj.), from signum "identifying mark, sign" (see sign (n.)) + combining form of facere "to make, to do" (from PIE root *dhe- "to set, put"). Intransitive sense of "to be of importance" is attested from 1660s. Meaning "engage in mock-hostile banter" is African-American vernacular, by 1932.
...'signifying,' which in Harlemese means making a series of oblique remarks apparently addressed to no one in particular, but unmistakable in intention in such a close-knit circle. ["Down Beat," March 7, 1968]