'calm' originates from Old French, specifically the word 'calme', where 'calme' meant 'quiet' or 'still'.

'calm' changed from Old French 'calme' and Middle English forms and eventually became the modern English word 'calm'; 'calmer' developed as the comparative/adjectival and noun form in English.

Initially related to Old French sense of 'quiet, still' (with older links to Latin/Greek roots often associated with heat or stillness), and over time its meaning settled into the modern sense of 'tranquil' or 'to make tranquil'.