'uneven-sided' originates from Modern English, specifically a compound of 'uneven' and 'side', where the prefix 'un-' meant 'not' and 'side' meant 'edge or boundary'.

'uneven' developed from Old English components: the negative prefix 'un-' plus 'even' (from Old English 'efen' via Middle English), while 'side' comes from Old English 'sīde'. These elements were combined in Modern English to form compounds like 'uneven-sided'.

Initially it described something 'not even' in a general sense; over time it retained that sense but became used specifically to describe objects or shapes whose sides are unequal ('having sides that are not equal').