" Catgut is a type of surgical thread made from the intestines of cows or sheep.” “So why do they call it catgut?” asked Rizzoli. “It goes back to the Middle Ages, when gut strings were used on musical instruments. The musicians referred to their instruments as their kit, and the strings were called kitgut. The word eventually became catgut. "

― Tess Gerritsen , The Surgeon (Rizzoli & Isles, #1)