Kühne, a German physiologist, was studying the digestion of proteins by the stomach enzyme pepsin. He originally used the term "ferment" to describe these substances, but he later changed it to "enzyme" to distinguish it from other types of ferments.

The word "enzyme" comes from the Greek word "en zyme," which means "in leaven." This reflects the fact that enzymes are biological catalysts that speed up chemical reactions in living organisms.