Great Britain vs never-never

Great Britain and never-never both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
never-never	Yes	No	No	No

Great Britain (noun)	never-never (noun)
an island comprising England and Scotland and Wales	installment plan
a monarchy in northwestern Europe occupying most of the British Isles; divided into England and Scotland and Wales and Northern Ireland; `Great Britain' is often used loosely to refer to the United Kingdom