'pro-establishment' is formed from the prefix 'pro-' (from Latin 'pro' meaning 'for') combined with 'establishment' (the noun formed from 'establish' + '-ment').

'Establish' entered English via Old French 'establir' (from Latin roots related to 'stabilis' meaning 'stable'); 'establishment' (the noun) developed from that verb in Middle English. The prefix 'pro-' comes directly from Latin 'pro' and was attached in modern English to form the compound adjective 'pro-establishment'.

Originally 'establishment' primarily denoted the act or result of establishing; over time it came to refer to the dominant social or political order ('the establishment'), and 'pro-establishment' came to mean 'in favor of that dominant order'.