significant (adj.)

late 13c., signifien, "be a sign of (a fact or alleged fact), indicate, mean," also "declare, make known by signs, speech, or action," 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").

The intransitive sense of "be of importance" is attested from 1660s. The meaning "engage in mock-hostile banter" is African-American vernacular, by 1932. Related: Signified; signifying.

While writing this essay, I asked a colleague, Dwight Andrews, if he had heard of the Signifying Monkey as a child. "Why, no" he relied intently. "I never head of the Signifying Monkey until I came to Yale and read about him in a book." I had been signified upon. If I had responded to Andrews, "I know what you mean; your Mama read to me from that same book the last time I was in Detroit," I would have signified upon him in return. [Henry Louis Gates Jr., footnote in "Figures in Black," 1987]

"serving as an external sign or symbol of some fact," c. 1400, significatif, "having meaning, meaningful," from Latin significativus, from significat-, stem of significare "make known, indicate" (see signify). Related: Significatively.

1650s, "without meaning," also "answering to no purpose," from in- (1) "not, opposite of" + significant. From 1748 as "small in size." Related: Insignificantly.