The quest for a vaccine against SARS-CoV-2 is likely to extend beyond this year. The search for the origins of the word “vaccine” takes us back to the end of the 18th century, when the highly infectious and devastating disease of the time was smallpox, caused by the variola virus. “Variola” refers both to the lesions and the disease itself – from the post-classical Latin “ pustule , pox ”, deriving from varus (“pimple”). Smallpox was a common infection for centuries – noted in 3rd century BC Egyptian mummies and in early descriptions from 4th century China and 7th century India, and spreading across the globe through trade and colonisation. It was dreaded for its high mortality rate and disfiguring effects. Notably, immunisations against disease, as we now know them, were not a reality. That is, until 1796, when English physician Edward Jenner observed how people previously infected with cowpox from cows, especially dairy workers, were unafflicted by smallpox’s oozing lesions, save for pustules on their hands. He injected matter from a dairy maid’s cowpox pustule into an eight-year-old boy, who was, six weeks later, variolated with smallpox but showed no infection. Jenner’s 1798 report documented variolae vaccinae (“cow-pox”) – from the Latin vaccinus (“from cows”), from the Latin vacca (“cow”) – and vaccine inoculation, thus giving the world both procedure and word. While the term vaccination was originally used in reference to smallpox, Louis Pasteur in 1881 proposed generalising it to encompass all protective immunisation procedures. The advent of vaccination brought its critics. The words “anti-vaccinator” and “anti-vaccinationist” appeared in 1806 and 1876, respectively, in British scientific and medical journals, with clipped versions “anti-vac” and “anti-vacc” emerging in the late 19th century. These terms have, in the past decade, evolved to anti-vax and anti-vaxxer, and are used more specifically in reference to opponents of influenza and MMR (measles-mumps-rubella) vaccinations. Orthographically, the letter “x” faithfully preserves the “ks” consonants in the middle of the word “vaccine”. More significantly, replacing the conventional “c” with the relatively rarer (in English) “x” not only renders it more eye-catching, it also indexes a negative value on the term, connoting a censorial effect. Returning to vaccine’s roots, recent research by virologist José Esparza and colleagues has furthered other studies, as well as Jenner’s own investigations, that suggest the contemporary virus used for the smallpox vaccine may well have also been derived from another, related virus – horsepox. If the origin “from horses” – the Latin equinus , from the Latin equus (“horse”) – had also been better recognised, then it might be equines and equination that we speak of now.