trainman vs brakeman

trainman and brakeman both are nouns.

Word	Noun	Adjective	Verb	Adverb
trainman	Yes	No	No	No
brakeman	Yes	No	No	No

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

Other hyponyms of trainman include signalman, yardman, train dispatcher, trainmaster, yardmaster.

trainman (noun)	brakeman (noun)
an employee of a railroad	a railroad employee responsible for a train's brakes