'antimasker' originates from Modern English, specifically the elements 'anti-' (from Greek 'anti' meaning 'against'), 'mask' (from Middle French 'masque' / Italian 'maschera', originally from medieval Latin/Old Italian referring to a mask or disguise), and the agentive suffix '-er' meaning 'person who does or is associated with'.

'antimasker' was formed in the early 21st century (notably during the COVID-19 pandemic) by compounding 'anti-' + 'mask' and adding the suffix '-er'; it developed from earlier compounds such as 'anti-mask' and the hyphenated 'anti-masker' into the solid-word form 'antimasker' in some usages.

Initially used simply to describe opposition to masks ('against masks'), it evolved into a label for people or activists who refuse masks or oppose mask mandates, carrying social and political connotations.