late 14c., "existing only in imagination," from Middle French fantastique (14c.), from Medieval Latin fantasticus, from Late Latin phantasticus "imaginary," from Greek phantastikos "able to imagine," from phantazein "make visible" (middle voice phantazesthai "picture to oneself"); see phantasm. Trivial sense of "wonderful, marvelous" recorded by 1938. Old French had a different adjective form, fantasieus "weird; insane; make-believe." Medieval Latin also used fantasticus as a noun, "a lunatic," and Shakespeare and his contemporaries had it in Italian form fantastico "one who acts ridiculously."
