Why did exposure to cowpox protect people from smallpox and how is that reflected in the origin of the word "vaccine"?

Cowpox infection produced a stronger inflammatory response that destroyed smallpox virus upon exposure, and "vaccine" was coined from the region where early users of the method lived

Cowpox virus shares antigenic components with smallpox, inducing cross‑protective immune memory; the term vaccine comes from Latin vaca, meaning cow, because the material came from cows

Cowpox and smallpox were identical viruses but cowpox reproduced more slowly, teaching the immune system to tolerate poxviruses; "vaccine" comes from the Latin for cow because cows were used as carriers

Cowpox provided passive antibodies that lasted for life against smallpox, and the word vaccine originates from the Greek for protection because ancient Greeks discovered the method