Vaccine
Etymology
From Latin "vaccinus" (of or from cows), from "vacca" (cow). Edward Jenner found in the 1790s that exposure to cowpox — "variolae vaccinae" — protected against smallpox. Louis Pasteur later generalized the term to honor Jenner, so every vaccine carries a hidden cow.
noun · /vak-SEEN/
A preparation that trains the immune system to recognize a germ without causing the disease.
What it names
Use it for the rehearsal — showing the body a threat in safe form so it’s ready for the real thing.
Example
The flu vaccine changes yearly because the virus it rehearses keeps mutating.
Related idea
A vaccine is the preparation you receive; the immunity it produces is the protection your body then builds. Vaccination is prophylactic — given before exposure to prevent — unlike a therapy, which treats an illness already underway.