'anticonstitutional' originates from Modern English, formed by the Greek prefix 'anti-' (from Greek 'anti') meaning 'against' combined with 'constitutional' (from 'constitution').

'constitution' comes from Latin 'constituere' (to set up, establish), passed into Old French as 'constitution' and then into Middle English as 'constitution'; the adjective 'constitutional' developed from that, and in Modern English 'anticonstitutional' was created by prefixing 'anti-'.

Initially 'constitution' meant 'a setting up' or 'establishment'; over time it came to mean the fundamental law or system of government, and 'anticonstitutional' evolved to mean 'against that fundamental law' or 'in violation of the constitution'.