'commensurability' originates from Latin, specifically the Medieval Latin word 'commensurabilitas' (related to 'commensurabilis'), where 'com-' meant 'together' and 'mensura' meant 'measure'.

'commensurabilitas' passed through Medieval Latin into late Middle English as 'commensurable' (adj.) and later formed the abstract noun 'commensurability' in modern English.

Initially, it meant 'capable of being measured by a common measure'; over time the sense remained in mathematics but extended into general and philosophical use to mean 'capable of fair comparison' or 'comparable by a common standard'.