'antimagistratical' originates as the prefix 'anti-' (from Greek 'anti' meaning 'against') combined with 'magistratical', ultimately from Latin 'magistratus' meaning 'magistrate' or 'office of a magistrate'.

'magistratus' (Latin) gave rise to Old French and Middle English forms 'magistrat' / 'magistrate'; the adjective 'magistratical' ('relating to a magistrate') developed in English, and adding the prefix 'anti-' produced 'antimagistratical' to denote opposition to the magistracy.

Initially formed to mean 'against the magistracy' in a literal sense; its usage has remained narrowly descriptive of opposition or hostility toward magistrates or their authority, often with a political or polemical tone.