I myself would ordinarily not consult the opinions expressed by Charles Harrington Elster in
The Big Book of Beastly Mispronunciations: The Complete Opinionated Guide for the Careful Speaker, because I go by the principle that usage is king and he appears to scorn that principle. However, on the
history of the pronunciation, Elster says that the preferred pronunciation in American English of
fracas given in dictionaries was FRAY-kus until Webster's Third New International Dictionary (1961) listed FRAK-us as a variant.
The Century Dictionary, an American dictionary of 1895, does indeed give FRAY-kus as the only English one, while marking the silent-
s pronunciation as French.
Elster prefers the FRAY-kus pronunciation, and quotes an author (Holt, 1937) as agreeing on that point:
Unduly influenced by La Belle France...the British struggle with "frack"ah.... We sensibly rhyme it with "Make us!"