'anterointerior' is formed from the combining prefix 'antero-' (from Latin 'ante' meaning 'before' or 'front') plus the Latin adjective 'interior' meaning 'inner'.

'antero-' derives from Latin 'ante' and entered English via Medieval/Scientific Latin as a combining form; 'interior' comes from Latin 'interior' (comparative of 'interus'/'inter' meaning 'within' or 'between'), and the two elements have been compounded in modern anatomical/medical English to form 'anterointerior'.

Initially composed simply to denote 'front' ('antero-') and 'inner' ('interior'); over time the compound has been used specifically in anatomical contexts to indicate a position that is both toward the front and the inner side.