nationalize v.

"of or pertaining to a nation or a country regarded as a whole; established and maintained by the nation; peculiar to the whole people of a country," 1590s, from French national (16c., from Old French nacion), and also from nation + -al (1). Opposed to local or provincial (or in the U.S., state).

Meaning "peculiar or common to the whole people of a country" is by 1620s. From 1802 as "established and maintained by the nation or its laws." As a noun, "citizen of a (particular) nation," from 1887. Related: Nationally. 

National guard is from 1793, originally in reference to an armed force in France identified with the revolution; U.S. use is from 1847, originally a name sometimes given to the organized militia. National anthem is recorded by 1806. 

A King though he's pestered with cares,

    For the most part he's able to ban them;

But one comes in a shape he never can escape—

    The implacable National Anthem!

[W.S. Gilbert, "His Excellency," 1894] 

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.