Worcestershire sauce is a fermented sauce first made in the 1830's. As is often the case, the sauce came about by accident (or chance).
When it was first produced by chemists in Worcester, England, the result was thought to be way too strong. It was banished to the basement of the Lea & Perrins building in a wooden barrel. Some years later, the basement was being organized, and the chemists happened back upon the barrel. They tried the sauce and this time it was quite good, having fermented and mellowed in the barrel.
The rest is history, and we see Worcestershire sauce everywhere today. It brings a nice snap to Bloody Marys and any other drink with tomato juice in it.