'attemper' originates from Latin, specifically the word 'temperare' (with an assimilated prefix from 'ad-' to 'at-'), where 'ad-' meant 'toward' and 'temperare' meant 'to mix, to make of proper proportion, to moderate'.

'attemper' passed into Old French as 'atemperer' (or Anglo-French forms), then into Middle English as 'atemperen'/'atemperen', and eventually became the modern English verb 'attemper'.

Initially, it meant 'to temper or mix to a proper proportion' (often in contexts like metallurgy or mixing); over time the meaning broadened to 'moderate, adjust, or lessen intensity' in general contexts.