'non-emetic' is a modern English compound formed from the prefix 'non-' (from Latin 'non', meaning 'not') attached to 'emetic' (from Greek 'emētikós', via Late Latin 'emetĭcus').

'emetic' entered English from Late Latin 'emetĭcus', which came from Greek 'emētikós' (from the verb 'emein', meaning 'to vomit'). The negative compound 'non-emetic' is a later English formation using the productive prefix 'non-'.

Originally 'emetic' meant 'causing vomiting' (from Greek); the compound 'non-emetic' has the straightforward negative meaning 'not causing vomiting', which has remained stable in medical usage.