Catgut used for surgical stitching comes from what animal?

Catgut, while sounding like it comes from cats, actually comes from the intestines of sheep, goats, or sometimes cattle.

It's a bit of a misnomer, as the name comes from the Middle Ages when the material was often made from the intestines of cats. However, modern surgical catgut is made from the submucosal layer of the intestines of the animals mentioned above.