'antiprecipitin' originates from a combination of Greek/Neo-Latin elements: the prefix 'anti-' (from Greek 'anti', meaning 'against') and 'precipitin' (a term formed in immunology from 'precipitate' + protein suffix '-in', meaning a substance causing precipitation).

'precipitin' itself was formed from the verb 'precipitate' (from Latin 'praecipitare', from 'prae-' meaning 'before' and 'caput' meaning 'head') and was adopted in immunology to name antibodies that cause precipitation; 'antiprecipitin' subsequently arose by prefixing 'anti-' to 'precipitin' to denote an antibody acting against or inhibiting a precipitin.

Initially the components conveyed 'against' + 'a substance that causes precipitation'; over time the compound came to be used in immunology to mean specifically 'an antibody that opposes or neutralizes a precipitin/precipitin reaction'.