'pro-narcotic' originates from combining the Latin prefix 'pro-' (from Latin 'pro' meaning 'for') and the word 'narcotic', which ultimately comes from Greek 'narkōtikos' (from Greek 'narkē' meaning 'numbness').

'narcotic' passed into English via Latin 'narcoticus' and Old/Middle French 'narcotique' from Greek 'narkōtikos'; 'pro-' comes directly from Latin 'pro' meaning 'for'. The compound 'pro-narcotic' is a modern English formation created by joining these elements.

Initially, 'narcotic' referred to substances that produce numbness or stupor; over time it broadened to mean drugs with sedative or psychoactive effects. Adding the prefix 'pro-' gives the sense 'in favor of', so 'pro-narcotic' means 'in favor of narcotics'.