'psalmist' originates from Greek, specifically the word 'psalmos', where the verb 'psallein' meant 'to pluck' (to play a stringed instrument); the agent suffix '-ist' comes via Latin/French meaning 'one who'.

'psalmist' changed from Greek 'psalmos' to Latin 'psalmus', passed into Old French as 'psaume' and Middle English as 'psalme' (meaning 'a song' or 'hymn'), and the modern English agent-form 'psalmist' developed to mean 'one who sings or composes psalms'.

Initially, it meant 'a song or hymn' (the 'psalm'), but over time it evolved into the meaning 'one who sings or composes psalms'.