To The Hilt is an amazingly comprehensive resource about sword swallowing: history, x-rays, videos, music, cartoons, terminology, and much more. There's even information about the Sword Swallowers Association International, "an elite private organization dedicated to networking existing sword swallowers around the world, promoting dialogue between sword swallowers, encouraging safe swordswallowing practices and techniques, and preserving and promoting the art of swordswallowing worldwide." From the history page:
Sword swallowing originated thousands of years ago in India by fakirs and shaman priests who developed it, along with fire-walking on hot coals, snake handling, and other ascetic religious practices, as demonstration of their invulnerability, power, and connection with their gods. Sword swallowing is still popular in certain parts of India, and there is said to be a tribe of sword swallowers in the state of Andhra Pradesh who pass down the art of sword swallowing from father to son.
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