c.1300, fantum "illusion, unreality," from Old French fantosme (12c.), from Vulgar Latin *fantauma, from Latin phantasma "an apparition" (see phantasm). The ph- was restored in English late 16c. (see ph). Meaning "specter, spirit, ghost" is attested from late 14c.; that of "something having the form, but not the substance, of a real thing" is from 1707. As an adjective from early 15c.