'gem' originates from Old French, specifically the word 'gemme', ultimately from Latin 'gemma' meaning 'bud' and 'precious stone'.

'gem' changed from Latin 'gemma' to Old French 'gemme' and then entered Middle English as 'gemme', eventually becoming the modern English word 'gem'.

Initially it meant 'bud' or 'bud-like object' and 'precious stone'; over time it came to mean specifically a 'precious stone' and by extension 'something excellent'.