sandman vs brownie

sandman and brownie both are nouns.

Word	Noun	Adjective	Verb	Adverb
sandman	Yes	No	No	No
brownie	Yes	No	No	No

As nouns, brownie is a hypernym of sandman; that is, brownie is a word with a broader meaning than sandman:

sandman: an elf in fairy stories who sprinkles sand in children's eyes to make them sleepy
brownie: (folklore) fairies that are somewhat mischievous

Other hypernyms of sandman include elf, gremlin, hob, imp, pixie, pixy.

sandman (noun)	brownie (noun)
an elf in fairy stories who sprinkles sand in children's eyes to make them sleepy	square or bar of very rich chocolate cake usually with nuts
	(folklore) fairies that are somewhat mischievous