significative 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]

1570s, "having or conveying a meaning," from Latin significantem (nominative significans), present participle of significare "make known, indicate" (see signify). Earlier in the same sense was significative; also significate (adj.) "indicated, signified"(early 15c.).

From 1590s as "serving as a sign or indication." Often "having a special or secret meaning," hence "important, weighty" (1761). Related: Significantly. The scientific significant figure is from 1680s. Significant other is attested by 1961, in psychology, "the most influential other person in the patient's world."