'nonantigenic' is formed from the negative prefix 'non-' (from Latin 'non', meaning 'not') + 'antigenic' (from 'antigen' + the adjectival suffix '-ic'). 'Antigen' was coined from the idea of an 'antibody generator' (ANTI + GEN).

'antigen' originated in early 20th-century immunology as a term for a substance that induces antibody production (coined from 'antibody generator'); 'antigenic' derived from 'antigen' with the suffix '-ic'; the modern compound 'nonantigenic' arose by adding the productive negative prefix 'non-' in 20th-century biomedical usage to indicate absence of antigenic properties.

Originally, 'antigen' carried the sense of a substance that generates antibodies; over time it broadened to mean any substance recognized by the immune system (binding antibodies or T cells). 'Nonantigenic' therefore evolved to mean 'lacking antigenic properties' or 'not eliciting a specific immune response.'