'posterior-dorsally' originates from Latin and Old English elements: Latin 'posterus' (posterior) where 'post-' meant 'after' and Latin 'dorsum' (dorsal) where 'dors-' meant 'back', combined with the adverbial suffix '-ly' from Old English '-lic' meaning 'having the quality of' or 'in the manner of'.

'posterior' passed from Latin 'posterus' through Medieval Latin and Middle English to modern English 'posterior'; 'dorsal' comes from Latin 'dorsum' → Medieval Latin 'dorsalis' → English 'dorsal'. Compounded anatomical terms (e.g., 'posterodorsal', hyphenated forms) arose in scientific Latin/English usage to specify combined directions.

Initially the components meant 'coming after' (posterior) and 'back' (dorsal); over time they were combined in anatomical usage to mean 'toward the back and rear surface' as expressed now by 'posterior-dorsally'.