Entries linking to fantasize
early 14c., "illusory appearance," from Old French fantaisie, phantasie "vision, imagination" (14c.), from Latin phantasia, from Greek phantasia "power of imagination; appearance, image, perception," from phantazesthai "picture to oneself," from phantos "visible," from phainesthai "appear," in late Greek "to imagine, have visions," related to phaos, phōs "light," phainein "to show, to bring to light" (from PIE root *bha- (1) "to shine").
Sense of "whimsical notion, illusion" is pre-1400, followed by that of "fantastic imagination," which is first attested 1530s. Sense of "day-dream based on desires" is from 1926. In early use in English also fantasie, phantasy, etc. As the name of a fiction genre, by 1948.
word-forming element used to make verbs, Middle English -isen, from Old French -iser/-izer, from Late Latin -izare, from Greek -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached.
The variation of -ize and -ise began in Old French and Middle English, perhaps aided by a few words (such as surprise, see below) where the ending is French or Latin, not Greek. With the classical revival, English partially reverted to the correct Greek -z- spelling from late 16c. But the 1694 edition of the authoritative French Academy dictionary standardized the spellings as -s-, which influenced English.
In Britain, despite the opposition to it (at least formerly) of OED, Encyclopaedia Britannica, the Times of London, and Fowler, -ise remains dominant. Fowler thinks this is to avoid the difficulty of remembering the short list of common words not from Greek which must be spelled with an -s- (such as advertise, devise, surprise). American English has always favored -ize. The spelling variation involves about 200 English verbs.