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.