'anti-scientifically' originates from Modern English, built from the prefix 'anti-' (from Greek 'antí' meaning 'against'), the adjective 'scientific' (from Latin 'scientificus', from 'scientia' meaning 'knowledge'), and the adverbial suffix '-ally' (from Latin/Old French adjective-to-adverb formation).

'anti-' entered English via Latin and French as a productive prefix meaning 'against'; 'scientific' came into English in the early 19th century from French 'scientifique' (from Latin 'scientificus'); the adverb 'anti-scientifically' arose by adding the adverbial suffix '-ally' to the adjective 'anti-scientific', producing the modern English adverb.

Initially the components meant 'against' + 'knowledge' (i.e. opposed to knowledge or learning), and over time the compound evolved to mean specifically 'opposed to or rejecting scientific methods or evidence.'