'anti-parliamentarian' is built from the prefix 'anti-' (from Greek 'anti-' meaning 'against') + 'parliamentarian' (from 'parliament' + suffix '-arian'). 'Parliament' entered English from Old French 'parlement', from parler 'to speak'.

'parliament' came from Old French 'parlement' (a discussion or speaking) ultimately from Latin roots related to 'speak'; 'parliamentarian' developed in English to mean a supporter or member of parliament, and the compound with 'anti-' formed to indicate opposition: 'anti-' + 'parliamentarian' → 'anti-parliamentarian'.

Originally, 'parliamentarian' referred simply to a member or supporter of a parliament; adding the prefix 'anti-' produced a straightforward opposite meaning 'against parliament' or 'against parliamentary rule', which has remained consistent in modern usage.