'anorectal' originates from the combining form 'ano-' and the adjective 'rectal', specifically 'ano-' ultimately from Latin 'anus' (meaning 'ring, anus') and 'rectal' from Latin 'rectus' / 'rectum' (meaning 'straight' or 'straight thing').

'anorectal' was formed in medical English by combining the prefix 'ano-' (from Latin 'anus') with 'rectal' (from Late Latin 'rectalis', from Latin 'rectus'/'rectum'); the elements 'rectum' and its adjective form 'rectal' entered English via Late Latin/Medieval Latin and then combined with 'ano-' in modern medical compounds.

Initially the elements meant 'anus' and 'straight (thing)', but over time the compound came to mean 'relating to the anus and rectum' in clinical/medical usage.