'pro-immigrant' is a compound formed from the prefix 'pro-' (from Latin 'pro', meaning 'for' or 'in front of') and 'immigrant' (from Latin-derived 'immigrant', meaning 'one who moves into a country').

'pro-' entered English from Latin via Old French and Late Latin uses; 'immigrant' comes from Latin 'immigrare' (in- 'into' + migrare 'to move') through French 'immigrer' and later English 'immigrant'. The compound 'pro-immigrant' is a modern English formation using the productive prefix 'pro-' plus the noun.

Initially, 'pro-' simply meant 'for' and 'immigrant' meant 'one who moves into a country'; combined, the modern compound came to mean 'in favor of immigrants or immigration policies', a political/attitudinal sense used in contemporary discourse.