Ah, Worcestershire sauce. A condiment from which, in my house, no steak can hide. Worcestershire sauce is also commonly used in the Caesar Salad and in Chex Mix.
The Worcestershire in Worcestershire sauce is most properly pronounced /ˈwʊstəˌʃɪər/, or something along the lines of "woostahsure" and is named such due to its creation in Worcester, England. Worcestershire sauce was originally created by Lea and Perrins in the 1830s.
Worcestershire sauce (that is to say, real, Lea & Perrins, Worcestershire sauce) is neither vegetarian nor vegan due to it containing anchovies. But, then again, there's not a whole lot for a vegetarian to put Worcestershire sauce on, anyway.
XWiz says: It is generally pronounced 'wuster', and anyone who pronounces it 'wustershire' would immediately be pounced on and beaten about the head and legs. I'm going to have to beg to differ with you on that one. Were it pronounced 'wuster', it would be Worcester sauce, which, while a perfectly cromulent synonym of Worcestershire sauce, is a different word entirely.