'unequal-dimensioned' originates from Modern English, specifically formed by combining the adjective 'unequal' (from Old French 'inegal' < Latin 'in-' + 'aequalis', where 'in-' meant 'not' and 'aequalis' meant 'equal') and the participial adjective 'dimensioned' (from Latin 'dimensio' via Old French 'dimension', where the root 'mens-' related to 'measure').

'unequal-dimensioned' is a modern compound: 'unequal' developed into Middle and Modern English from Old French and Latin roots, while 'dimension' came into English from Latin 'dimensio' through Old French 'dimension'; the adjectival form 'dimensioned' was created in Modern English by adding the past-participial suffix '-ed' to 'dimension'.

Initially, 'unequal' meant 'not equal' and 'dimensioned' meant 'having dimensions'; over time, when combined, the compound took on the specific technical sense 'having dimensions that are not equal', used particularly in engineering and descriptive contexts.