The word 'vaccine' originates from the Latin vacca for "cow." This direct link is due to the pioneering work of Edward Jenner in the late 18th century, who used the cowpox virus (Variolae vaccinae) to create immunity against the deadly smallpox. The term was initially specific to this cowpox-derived preparation but was later generalized by Louis Pasteur in the 1880s to honor Jenner's discovery. It now broadly denotes any biological preparation that provides active acquired immunity to a particular infectious disease, tracing a clear path from its literal bovine origin to its modern, abstract medical meaning.

Structure: vacc (cow) + ine (substance of/related to) vacc (from Latin vacca, meaning "cow"); ine (a suffix of French/Latin origin used to form nouns, often meaning "of or pertaining to," "made of," or "a substance").