'postero-anteriorly' originates from New/medical Latin, specifically combining the prefix 'postero-' (from Latin 'posterus'/'posterior') and the adjective 'anterior' (from Latin 'ante'), where 'posterus' meant 'coming after, (back)' and 'ante' meant 'before (front)'.

'postero-anteriorly' developed as the adverbial form of the compound adjective 'postero-anterior', itself created in medical Latin from the Latin words 'posterior' and 'anterior', and entered English medical usage in modern times.

Initially it referred generally to relationships of posterior and anterior (positions or aspects); over time it became used specifically to indicate direction or imaging taken 'from the posterior toward the anterior' (from back to front).