antique (adj.)

1520s, antick, antyke, later antique (with accent on the first syllable), "grotesque or comical gesture," from Italian antico "antique," from Latin antiquus "old, ancient; old-fashioned" (see antique (adj.)). In art, "fantastical figures, incongruously combined" (1540s).

Originally (like grotesque) a 16c. Italian word referring to the strange and fantastic representations on ancient murals unearthed around Rome (especially the Baths of Titus, rediscovered 16c.); later extended to "any bizarre thing or behavior," in which sense it first arrived in English. As an adjective in English from 1580s, "grotesque, bizarre." In 17c. the spelling antique was restricted to the original sense of that word.

Anticke worke, A worke in painting or carving of divers shapes of Beasts, Birds, Flowers, &c. unperfectly mixt, and made one of another. [Cockeram, English Dictionarie, 1623]

a collector's word for old advertisements, by 1974, from advertisement + antique.