Christmas cake vs fruitcake

Christmas cake and fruitcake both are nouns.

Word	Noun	Adjective	Verb	Adverb
Christmas cake	Yes	No	No	No
fruitcake	Yes	No	No	No

As nouns, fruitcake is a hypernym of Christmas cake; that is, fruitcake is a word with a broader meaning than Christmas cake:

Christmas cake: a rich fruitcake (usually covered with icing and marzipan) and eaten at Christmas
fruitcake: a rich cake containing dried fruit and nuts and citrus peel and so on

Christmas cake (noun)	fruitcake (noun)
a rich fruitcake (usually covered with icing and marzipan) and eaten at Christmas	a rich cake containing dried fruit and nuts and citrus peel and so on
	a whimsically eccentric person