sterilize v.

mid-15c., "barren," from Old French stérile "not producing fruit" and directly from Latin sterilis "barren, unproductive, unfruitful; unrequited; unprofitable," from PIE *ster- "lacking, sterile," source also of Sanskrit starih "a barren cow," Greek steira "sterile, infertile" (of a cow, goat, woman), Armenian sterj "infertile," perhaps ultimately from root *ster- (1) "stiff." Originally in English with reference to soil; of persons (chiefly females), from 1530s. The sense of "sterilized, free from living germs" is first recorded 1877.

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.