'unequal-angled' originates from Modern English, formed by combining the prefix 'un-' (from Old English 'un-') meaning 'not', the adjective 'equal' (from Old French 'egal' ultimately from Latin 'aequalis'), and 'angled' derived from 'angle' (from Old French 'angle', from Latin 'angulus') where 'angulus' meant 'corner'.

'unequal-angled' developed from the descriptive phrase 'unequal angle' and later became a hyphenated compound in technical and descriptive English usage to qualify shapes as 'unequal-angled'.

Initially it denoted simply 'not equal in angle'; over time it has remained a technical descriptive term used in geometry and shape description with the same core sense.