witches' brew vs salmagundi

witches' brew and salmagundi both are nouns.

Word	Noun	Adjective	Verb	Adverb
witches' brew	Yes	No	No	No
salmagundi	Yes	No	No	No

As nouns, salmagundi is a hypernym of witches' brew; that is, salmagundi is a word with a broader meaning than witches' brew:

Other hypernyms of witches' brew include assortment, miscellanea, miscellany, mixed bag, mixture, motley, potpourri, smorgasbord, variety.

witches' brew (noun)	salmagundi (noun)
a fearsome mixture	cooked meats and eggs and vegetables usually arranged in rows around the plate and dressed with a salad dressing
	a collection containing a variety of sorts of things