Britishism vs Briticism

Britishism and Briticism both are nouns.

Word	Noun	Adjective	Verb	Adverb
Britishism	Yes	No	No	No
Briticism	Yes	No	No	No

As nouns, Britishism and Briticism are synonyms defined as:

Britishism and Briticism: an expression that is used in Great Britain (especially as contrasted with American English)

Other synonyms of Britishism include Anglicism.

Britishism (noun)	Briticism (noun)
a custom that is peculiar to England or its citizens	an expression that is used in Great Britain (especially as contrasted with American English)
an expression that is used in Great Britain (especially as contrasted with American English)