'pro-authoritarian' originates from Modern English compounding of the prefix 'pro-' (from Latin 'pro', meaning 'for') and 'authoritarian' (an English adjective formed from 'authority' + suffix '-arian').

'authoritarian' developed in English from 'authority' (from Old French 'autorité'), which in turn comes from Latin 'auctoritas' (from 'auctor', related to 'increase' or 'originator'). The prefix 'pro-' entered English from Latin 'pro' via Old French and Medieval Latin, and was later used productively in Modern English to form compounds like 'pro-authoritarian'.

Originally Latin 'auctoritas' meant 'influence, command, or prestige'; over time English 'authoritarian' came to describe a style of governance emphasizing strict obedience to authority and limited personal freedoms; 'pro-' adds the sense of being 'in favor of' that position.