1A word, phrase, or idiom of Old English origin; (hence) an Anglicism.
2US A word that is regarded as vulgar, considered (especially humorously) to be of traditional Anglo-Saxon origin, with allusion to the idea of an earlier, uncomplicated era of language and culture; a swear word.
3Identification with, or belief in the superiority of, England (or Britain), the English-speaking peoples, their civilization, culture, etc.
Early 19th century; earliest use found in The Quarterly Review. From Anglo-Saxon + -ism.