prioritize v.

late 14c., prioritie, "state of being earlier (than something else), prior occurrence or existence," from Old French priorite (14c.) and directly from Medieval Latin prioritatem (nominative prioritas) "fact or condition of being prior" (source also of Spanish prioridad), from Latin prior (see prior (adj.)).

From c. 1400 as "precedence in right, place, or rank." In 1897 Century Dictionary wrote "Priority is the state or fact of coming first in order of time; what little use it has beyond this meaning is only a figurative extension," but in 20c. the sense shifted toward "fact or condition of coming first in importance or requiring immediate attention; thing regarded as more important than another or others." Wycliffe (early 15c.) renders prioritas into (Middle) English as furtherhead.

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.