galley slave vs manual laborer

galley slave and manual laborer both are nouns.

Word	Noun	Adjective	Verb	Adverb
galley slave	Yes	No	No	No
manual laborer	Yes	No	No	No

As nouns, manual laborer is a hypernym of galley slave; that is, manual laborer is a word with a broader meaning than galley slave:

galley slave: a laborer who is obliged to do menial work
manual laborer: someone who works with their hands; someone engaged in manual labor

Other hypernyms of galley slave include jack, laborer, labourer.

galley slave (noun)	manual laborer (noun)
a slave condemned to row in a galley	someone who works with their hands; someone engaged in manual labor
a laborer who is obliged to do menial work