'antiskeptical' originates from Modern English, specifically formed from the prefix 'anti-' (from Greek 'antí') and the adjective 'skeptical' (from Greek 'skeptikos'), where 'anti-' meant 'against' and 'skeptikos' meant 'inquiring, inclined to doubt'.

'skeptical' entered English via Latin and French from Greek 'skeptikos'; the combining form 'anti-' has been used in English since the 17th century. 'antiskeptical' is a modern compound formed in English by joining these elements.

Initially the components meant 'against' + 'inquiring/doubting', so the compound originally implied 'against doubting' or 'opposed to skepticism'; in modern usage it denotes an attitude of not being skeptical or being inclined to accept claims.