'antimethodicalness' originates from a modern English formation combining the prefix 'anti-' (from Greek ἀντί, meaning 'against') with the adjective 'methodical' and the nominalizing suffix '-ness'.

'methodical' comes from 'method' (Late Latin/Old French via Latin 'methodus' from Greek 'methodos'), while the combining prefix 'anti-' was borrowed from Greek into English; these elements were joined in recent English to form 'antimethodical' and then nominalized to 'antimethodicalness'.

Initially, the component parts meant 'against' + 'ordered method'; over time the assembled modern coinage came to mean specifically 'the state or quality of being opposed to method' (the meaning remains consistent with its parts).