'annelidiform' originates from New Latin/Latin, specifically the word 'Annelida' and the Latin element '-formis', where 'Annelida' derives from Latin 'annellus' meaning 'little ring' and '-formis' meant 'shape' or 'form'.

'annelidiform' developed by combining the New Latin term 'Annelida' (used for ringed/segmented worms) with Latin '-formis' (later English '-form'/'-iform'), and became the modern English formation 'annelidiform' (i.e., 'annelid' + '-iform').

Initially the roots referred specifically to 'ringed' or 'little ring' structures; over time the combined formation came to mean 'having or resembling the form of an annelid' in scientific and descriptive usage.