Why is scoring zero at a game "love"?

When I was watching "The Prince of Tennis", when I heard the referee say 15-0, I have been very depressed why the English reading of the front 15 is so standard, and the following 0, how can I hear the pronunciation of the English word zero like 0? Sounds like love, but I didn't dare think of the word... Now I get it! Let's start with an allusion.