common man vs cypher

common man and cypher both are nouns.

Word	Noun	Adjective	Verb	Adverb
common man	Yes	No	No	No
cypher	Yes	No	Yes	No

As nouns, cypher is a hyponym of common man; that is, cypher is a word with a more specific, narrower meaning than common man:

common man (noun)	cypher (noun)
a person who holds no title	a secret method of writing
	a message written in a secret code
	a person of no influence
	a quantity of no importance; thing (object:), singular, negative pronoun; pronoun, thing, singular; quantifier: negative existential
	a mathematical element that when added to another number yields the same number

common man (verb)	cypher (verb)
	make a mathematical calculation or computation
	convert ordinary language into code