As the Covid-19 vaccine is rolled out, various politicians have volunteered to be injected with it live on TV, which might add to the gaiety of the nation as we celebrate this triumph of international science. Meanwhile let us remember that the word “vaccine” itself – from vacca, Latin for cow – encodes a triumphant moment in medical history.

The earliest method of inducing immunity against smallpox was called “variolation” (from Latin variola, pox or pustules), and involved snorting powdered smallpox scabs, or injecting smallpox pus beneath the skin. This method was inexact, and sometimes killed the patient. In 1796, the English doctor Edward Jenner instead inoculated (from Latin inoculare, to implant or graft) his gardener’s eight-year-old son, James Phipps, with the bovine form of the disease, cowpox, which subsequently made him immune to smallpox. So “vaccination”, or encowing, had arrived.

So, soon, did the anti-vaccination sceptics, though in the 19th century they were “anti-vaccers” or “anti-vac”. The modern form “anti-vaxxer” or “anti-vax” does not appear until the 2000s wave inspired by Andrew Wakefield’s MMR fraud. We are now advised to speak instead of the “vaccine hesitant” as we dream of the sunlit uplands of herd immunity, along with the cows.

• Steven Poole’s A Word for Every Day of the Year is published by Quercus.