'pro-smoking' is a compound formed from the prefix 'pro-' (from Latin 'pro' meaning 'for, on behalf of') and 'smoking', the gerund/participle form of the verb 'smoke'.

'pro-' comes from Latin 'pro' (meaning 'for'), while 'smoke' traces back to Old English 'smoca'/'smocian' (meaning 'smoke' or 'to emit smoke'), which developed into Middle and then Modern English 'smoke' and the present-participle 'smoking'. The compound 'pro-smoking' is a modern English formation using the prefix 'pro-' plus the gerund.

Initially, 'pro-' simply meant 'for' and 'smoking' referred to the act of emitting smoke; combined in modern usage they specifically denote being 'for' or supportive of the behavior or policies that permit smoking.