'anti-royalism' originates from the prefix 'anti-' (from Greek 'anti-' meaning 'against') combined with 'royalism' (from 'royal', ultimately from Old French 'roial' and Latin 'regalis', from 'rex' meaning 'king').

'royal' came into English via Old French 'roial' (Modern French 'royal'), from Latin 'regalis' (from 'rex' meaning 'king'); 'royal' produced 'royalism' (the doctrine/support of monarchy), and the prefix 'anti-' was attached in English to form 'anti-royalism' to express opposition to that doctrine.

Initially formed to mean 'opposition to royalism or monarchy', the term has retained that core meaning and is used to describe both the ideology and general opposition to royal institutions.