'posterior-lateral' originates from Latin components: specifically 'posterior' from Latin 'posterus' where 'posterus' meant 'coming after' or 'behind', and 'lateral' from Latin 'lateralis' (from 'latus') where 'latus' meant 'side'.

'posterior' passed from Latin 'posterus' into Late Latin and Middle English as 'posterior'; 'lateral' passed from Latin 'lateralis' (from 'latus') into Late Latin and Middle English as 'lateral'. The compound form (often as 'posterolateral' or hyphenated 'posterior-lateral') arose in modern medical/English usage to describe combined positional relations.

Initially the components meant 'behind' (posterior) and 'side' (lateral) separately; over time they were combined in anatomical contexts to mean 'toward the back and to the side' as a single locational descriptor.