packman vs sandboy

packman and sandboy both are nouns.

Word	Noun	Adjective	Verb	Adverb
packman	Yes	No	No	No
sandboy	Yes	No	No	No

As nouns, sandboy is a hyponym of packman; that is, sandboy is a word with a more specific, narrower meaning than packman:

packman: someone who travels about selling his wares (as on the streets or at carnivals)
sandboy: a young peddler of sand; used now only to express great happiness in `happy as a sandboy'

Other hyponyms of packman include chapman, cheapjack, crier, muffin man, transmigrante.

packman (noun)	sandboy (noun)
someone who travels about selling his wares (as on the streets or at carnivals)	a young peddler of sand; used now only to express great happiness in `happy as a sandboy'