'gem-set' is a compound formed from 'gem' + 'set'. 'Gem' originates from Old French 'gemme' and Latin 'gemma' meaning 'bud, jewel', while 'set' comes from Old English 'settan' meaning 'to place or put'.

'gem' comes from Latin 'gemma' → Old French 'gemme'; 'set' comes from Old English 'settan'. The combination into the compound adjective/verb 'gem-set' developed in Modern English by compounding the noun 'gem' with the verb 'set' to mean 'set with gems.'

Initially the separate words referred to a 'gem' (a jewel) and the action 'to set'; over time the compound came to mean specifically 'decorated or mounted with gems' as a single descriptive term.