'estimator' originates from English, formed from the verb 'estimate' (itself from Latin 'aestimare'), where the Latin root 'aestim-'/'aestimare' meant 'to value' or 'to appraise'.

'estimator' developed from Middle English forms of 'estimate' (Old French 'estimer' < Latin 'aestimare') and was later formed in Modern English by adding the agentive suffix '-or' to create 'estimator'.

Originally related to the basic sense 'to value or appraise' (from Latin 'aestimare'), the meaning broadened to 'one who makes an estimate' and in technical fields (especially statistics) to a 'rule or formula that provides an estimate'.