Just read this on Wikipedia. An interesting fact that I was not aware of before and another example of the mighty AVFC influencing our beautiful game.
"Added time was introduced because of an incident which happened in 1891 during a match between Stoke and Aston Villa. Trailing 1–0 and with just two minutes remaining, Stoke were awarded a penalty. Villa's goalkeeper kicked the ball out of the ground, and by the time the ball had been recovered, the 90 minutes had elapsed and the game was over"
What it doesn't say is that Sir Alex Rednose Fergiescum was the architect of the "phantom minutes" that are added to the end of a game until Man Ure score a winning goal!