1751, "render general, make more general, bring under a general description," probably a new formation from general (adj.) + -ize. Middle English had generalisen (early 15c.). Intransitive sense of "recognize that two or more objects have a common character; form a general notion" is from 1785. Related: Generalizable; generalized; generalizing.
Entries linking to generalize
c. 1200, "of wide application, generic, affecting or involving all" (as opposed to special or specific), from Old French general (12c.) and directly from Latin generalis "relating to all, of a whole class, generic" (contrasted with specialis), from genus (genitive generis) "stock, kind" (from PIE root *gene- "give birth, beget," with derivatives referring to procreation and familial and tribal groups).
What is common is of frequent occurrence. What is general admits of comparatively few exceptions: the general opinion (the opinion of the majority); the general welfare. [J.H.A. Günther, "English Synonyms Explained & Illustrated," Groningen, Netherlands, 1904]
Used in forming titles from late 14c. with the sense "having general authority or jurisdiction, chief." Phrase in general "without exception, in one body; as a rule, generally, not specifically" is from late 14c. General rule, one applying to an art or science as a whole, is from c. 1400. General store attested by 1810, American English, in reference to the range of goods sold; a general hospital (1737) is one not restricted to one class of persons or type of disease.
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.
Others are reading
this kind of infection generalizes throughout the immune system