muggins vs cuckoo

muggins and cuckoo both are nouns.

Word	Noun	Adjective	Verb	Adverb
muggins	Yes	No	No	No
cuckoo	Yes	No	Yes	No

As nouns, cuckoo is a hyponym of muggins; that is, cuckoo is a word with a more specific, narrower meaning than muggins:

muggins (noun)	cuckoo (noun)
a person who lacks good judgment	any of numerous European and North American birds having pointed wings and a long tail
	a man who is a stupid incompetent fool

muggins (verb)	cuckoo (verb)
	repeat monotonously, like a cuckoo repeats his call