'anteroposteriorly' originates from New Latin/Modern English, combining the prefix 'antero-' (from Latin 'ante', meaning 'before' or 'front') with 'posterior' (from Latin 'posterior', comparative of 'posterus', meaning 'coming after' or 'behind'), plus the English adverbial suffix '-ly'.

'anteroposterior' was formed in scientific/medical Latin and entered English as a compound term meaning 'relating to both anterior and posterior (front and back)'; the adverbial form 'anteroposteriorly' was created by adding the English suffix '-ly' to describe action or orientation along that axis.

Initially used to describe a positional relation of front and back (anteroposterior); over time it has been used as an adverb to indicate direction or orientation 'from front to back' along the anteroposterior axis.