'archmonarchist' originates from English, specifically a compound of the prefix 'arch-' and the noun 'monarchist'. The prefix 'arch-' derives from Greek 'arkhē/arkhos' meaning 'chief' or 'principal', and 'monarchist' ultimately comes from Greek 'monarkhēs' (via Latin and Old French) meaning 'one who supports a single ruler.'

'monarch' came into English via Old French 'monarque' and Latin 'monarcha' from Greek 'monarkhēs' ('mono-' meaning 'one' + 'arkhē' meaning 'rule'); 'monarchist' was formed in modern English (influenced by French 'monarchiste') to mean a supporter of monarchy. The combining prefix 'arch-' (from Greek 'arkhos') was later attached to form 'archmonarchist' in modern usage to indicate an extreme or principal monarchist.

Initially the elements meant 'chief' (arch-) + 'supporter of monarchy' (monarchist); over time the compound has been used to denote not just a leading monarchist but specifically an extreme or fervent advocate of monarchy.