If you're a fan of Tottenham Hotspur, you probably know fine well that the Hotspur in your team's name is said to be a reference to Sir Henry Percy, aka Harry Hotspur. However, that just begs the question - How did he get his name? Just what is a Hot Spur? Well, this might clear things up. It's from a 19th century dialect dictionary:

Hots, Huts: round balls of leather fastened to the sharp end of the spurs of fighting cocks

The spurs themselves were sharp, pointy, and very vicious. Putting a leather ball on the end would lessen the damage when you were training your bird.