'pro-clericalist' originates from Latin 'pro' (meaning 'for') combined with 'clericalist', which derives from 'clerical' + the agentive suffix '-ist'.

'clerical' comes from Old English 'clerc' (from Late Latin 'clericus'), which in turn comes from Greek 'klerikos' from 'kleros' ('lot, share'). The English formation 'clericalist' developed by adding the suffix '-ist' to 'clerical', and 'pro-' was prefixed to form 'pro-clericalist'.

Originally, the root 'kleros' referred to a 'lot' or 'share' and 'cleric' came to mean a member of the clergy; over time the compound 'pro-clericalist' came to mean specifically 'one who is for clerical influence or authority', especially in political contexts.