'posterior-superior' originates from Latin, specifically the words 'posterior' and 'superior', where 'posterior' meant 'coming after' (from Latin 'posterus') and 'superior' meant 'higher' or 'above' (from Latin 'superus').

'posterior' entered English via Late Latin/Medieval Latin (from Latin 'posterior', comparative of 'posterus'), and 'superior' entered via Medieval Latin (from Latin 'superior', comparative of 'superus'); the compound descriptive form 'posterior-superior' or 'postero-superior' developed in medical and anatomical Latin/English usage to combine the two directional senses.

Initially, the roots referred more generally to 'coming after' ('posterior') and 'higher/above' ('superior'); over time, in anatomical contexts these terms were combined to denote a precise position that is both toward the back and toward the upper part of the body.