The durable cord called "catgut" is known throughout the world for its use in the finest musical instruments and sports equipment. Until nylon began to replace it in many applications, it was quite prevalent. But, despite its name, catgut is sorely lacking in any cat based materials.
The origins of the word are steeped in mystery. Some explanations are more plausible than others, though they are all conjecture. What is known is that, rather than felines, it is created from the intestines of sheep or goat and occasionally cows, hogs, horse, mules or donkeys.
So rest assured that next time you're batting around a birdie, you won't be doing it with parts of the household pet.