Oh for Pete's sake, there was no Arab writer. Only someone with little familiarity with the period and literature and form or perhaps someone from the FE crowd would believe otherwise. Take a literature course, for Pete's sake...Just found this today
If you don't see him as a crusader and you don't believe it was written by an Arab, you will never see the whore as I see her.
We know this is all a jest, as is the very name of the historian: "Cide" is an honorific, "Hamete" is a version of the Arab name Hamid, and "Benengeli" means eggplant.
But this eggplantish historian is no more a jest than anything else in the novel, whether it is Don Quixote tilting at windmills or Sancho Panza governing an island not surrounded by water. Benengeli is, apparently, just as earnest as Don Quixote, just as peculiar and just as important to understanding what this novel is about.
At the time when Cervantes was writing this novel, nothing about this jest was possible. Neither an Arabic-speaking Moor nor a Hebrew-speaking Jew would have been readily found in the Toledo marketplace. And no Moor would have translated Arabic in the cloister of a church.
The Jews had been expelled from Spain in 1492; only converts remained. Books in Arabic had been burned with all the ferocity that the priest applies to Don Quixote's library of chivalric narratives. And while the Muslims hadn't yet been expelled from Spain (that would happen in the years just after the first part of "Don Quixote" was published), they too had to convert.
So Spain was full of New Christians: converts from Islam (called moriscos) and Judaism (called conversos), some continuing to secretly practice their religion (like the Jewish marranos). One reason that pork became such a popular Spanish dish was that eating it was a way to publicly prove one was not following the dietary rules of Islam or Judaism. Eggplant, however, was associated with Muslim and Jewish tastes back when Toledo was home to a flourishing Jewish community.
So Cervantes is up to a bit of mischief with these allusions.