c.1440, perhaps a shortening of O.Fr. pantaisier "to be out of breath" (12c.), probably from V.L. *pantasiare "be oppressed with a nightmare, struggle for breathing during a nightmare," lit. "to have visions," from Gk. phantasioun "have or form images, subject to hallucinations," from phantasia "appearance,
image, fantasy" (see phantasm). The noun is attested from c.1500.