caller-up vs verbalizer

caller-up and verbalizer both are nouns.

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

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

caller-up: the person initiating a telephone call
verbalizer: 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, utterer, verbaliser.

caller-up (noun)	verbalizer (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)