'uneven-jawed' originates from Modern English, specifically the combination of the adjective 'uneven' + noun 'jaw' + adjectival suffix '-ed', where 'uneven' meant 'not level or regular' and 'jaw' meant 'the lower facial bone or mouth framework'.

'uneven' developed in Middle English from the negative prefix 'un-' + Old English/Old Norse-rooted 'even' (meaning 'level'), while 'jaw' descends from older Germanic words for the cheek or jaw area; these elements were combined in modern usage to form the descriptive compound 'uneven-jawed'.

Initially the components separately meant 'not level' ('uneven') and 'lower facial bone' ('jaw'); over time the compound came to be used idiomatically to describe a person whose jaw or jawline appears asymmetrical ('having an irregular jawline').