In the early 1940s, Esmond Emerson Snell (1914-2003) was trying to figure out why baby chicks who were fed raw egg whites (I know.. how cruel..) showed symptoms of biotin deficiency despite having plenty of it in the diet.
So who's getting the biotin? Turned out the egg white itself just wouldn't release the biotin for the chicks to use. So Snell purified the protein that held the biotin so tightly, which is no small feat today and even harder to do back then. He called it 'avidin' (avid + biotin or 'hungry for biotin').
Snell said of his work: “The ability of this substance to take up and release biotin specifically and quantitatively suggests its possible use as a tool in the purification of biotin.”
He underestimated his contribution because this very strong and very reproducible interaction has become the foundation for probing all sorts of biological processes.