bargainer vs barrow-boy

bargainer and barrow-boy both are nouns.

Word	Noun	Adjective	Verb	Adverb
bargainer	Yes	No	No	No
barrow-boy	Yes	No	No	No

As nouns, barrow-boy is a hyponym of bargainer; that is, barrow-boy is a word with a more specific, narrower meaning than bargainer:

bargainer: someone who purchases and maintains an inventory of goods to be sold
barrow-boy: a hawker of fruit and vegetables from a barrow

bargainer (noun)	barrow-boy (noun)
someone who purchases and maintains an inventory of goods to be sold	a hawker of fruit and vegetables from a barrow
negotiator of the terms of a transaction