'posterior-dorsal' originates from modern English, formed by combining the Latin-derived adjectives 'posterior' and 'dorsal', where 'posterior' ultimately comes from Latin 'posterus' meaning 'coming after' and 'dorsal' comes from Latin 'dorsum' meaning 'back'.

'posterior' entered English via Latin (Late/Medieval Latin 'posterior', comparative of 'posterus'), and 'dorsal' is formed from Latin 'dorsalis' (from 'dorsum') in post-medieval anatomical usage; the hyphenated compound 'posterior-dorsal' is a modern anatomical/biological formation combining those elements.

Initially, 'posterior' meant 'coming after' and 'dorsal' meant 'back'; over time these terms were specialized in anatomy to indicate position, and together they now denote a position toward the rear and on the dorsal surface.