'antiskepticism' originates from Modern English, combining the prefix 'anti-' (from Greek 'anti' meaning 'against') with the noun 'skepticism' (ultimately from Greek 'skeptikos' via Latin and French).

'skepticism' changed from Greek 'skeptikos' (meaning 'inquisitive, reflective') into Latin and then Old French forms, entering English as 'skeptic'/'skepticism' in Modern English; the prefix 'anti-' (Greek 'anti') has long been used in English to form opposites, and together in Modern English they produced 'antiskepticism'.

Initially the elements meant 'against' + 'a reflective/inquiring attitude'; combined as 'antiskepticism' it denotes specifically an attitude or stance opposing skeptical doubt and often defending belief or certainty in particular claims.