pitchman vs muffin man

pitchman and muffin man both are nouns.

Word	Noun	Adjective	Verb	Adverb
pitchman	Yes	No	No	No
muffin man	Yes	No	No	No

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

pitchman: someone who travels about selling his wares (as on the streets or at carnivals)
muffin man: formerly an itinerant peddler of muffins

Other hyponyms of pitchman include chapman, cheapjack, crier, sandboy, transmigrante.

pitchman (noun)	muffin man (noun)
someone who travels about selling his wares (as on the streets or at carnivals)	formerly an itinerant peddler of muffins
an aggressive salesman who uses a fast line of talk to sell something