
Now, to pronunciation. Is it FRAY-kus? FRACK-us? What about frack-AH? Believe it or not, all three are correct, though the first two are more common in American English (FRAY-kus is the one we supply as an audio clip on our Dictionary page) and the last one is more common in British English.
To understand why, take a look at the path the word traveled into English. The Online Etymological Dictionary informs us fracas first appeared in Italy as fracassare, meaning "to smash or break in pieces." It was formed via a combination of fra, "a shortening of the Latin infra- 'below,'" and "the Italian cassare 'to break,' from Latin quassare 'to shake.'" Fracas then made its way into French in the 15th century, and three hundred years later began showing up in English — the earliest recorded use is in 1727.
Thus it makes sense that the Brits, living as close to the continent as they do, maintain the French pronunciation in their speech, while Americans tend to say it like they see it, as we all do when pronouncing the "t" in DuPont, or the "s" when referring to the capital of France.
If that's offensive to the French, then let them fracas away.