'temper' originates from Latin, specifically the word 'temperare', where the root meant 'to mix in proportion, to moderate or restrain'.

'temper' passed into Old French as 'temprer' (or similar forms) and Middle English as 'tempren'/'temper', eventually becoming the modern English word 'temper'.

Initially, it meant 'to mix in proper proportion or to moderate', and over time it broadened to include 'to moderate or soften (a quality)' and the noun sense 'state of mind or disposition' (especially relating to anger).