caller-up vs utterer

caller-up and utterer both are nouns.

Word	Noun	Adjective	Verb	Adverb
caller-up	Yes	No	No	No
utterer	Yes	No	No	No

As nouns, utterer is a hypernym of caller-up; that is, utterer is a word with a broader meaning than caller-up:

caller-up: the person initiating a telephone call
utterer: someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)

Other hypernyms of caller-up include speaker, talker, verbaliser, verbalizer.

caller-up (noun)	utterer (noun)
the person initiating a telephone call	someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)
	someone who circulates forged banknotes or counterfeit coins
	an organism that can utter vocal sounds