pudding head vs poor fish

pudding head and poor fish both are nouns.

Word	Noun	Adjective	Verb	Adverb
pudding head	Yes	No	No	No
poor fish	Yes	No	No	No

As nouns, pudding head and poor fish are synonyms defined as:

Other synonyms of pudding head include dolt, dullard, pillock, pudden-head, stupe, stupid, stupid person.

pudding head (noun)	poor fish (noun)
a person who is not very bright	a person who is not very bright