'cave-dweller' is a compound formed from the noun 'cave' and the agent noun 'dweller' (from the verb 'dwell'), used to denote someone who dwells in a cave.

'cave' entered English via Middle English from Old French and ultimately from Latin 'cavea' meaning 'hollow' or 'cavity'; 'dwell' comes from Old English 'dwellan'/'dwellan' (and related Germanic roots) meaning 'to remain, abide', producing the agent noun 'dweller' in Modern English; the compound 'cave-dweller' follows English patterns of forming compound nouns.

Originally the components referred simply to 'a person/animal living in a hollow or cave'; over time the compound also acquired figurative uses describing someone perceived as uncultured or out of touch.