Am Romanian, we also use Chinese for the same expression. That is most of the times, we also use Turkish, as in: “What it is so hard to understand? Am
I speaking Turkish to you?”
That's because we are still studying Greek and Latin on some public school.
A minority today, but one would assume (as in the case in e.g. German and France) more (of students) in the past 50-100-200 years when the phrase was established.
If you don't understand, you would say "Mi sembra arabo" (it seems arabic to me) but if you are talking and the other part doesn't understand it is more common "E che parlo, turco?" (what am I speaking, turkish?) than "E che parlo, arabo?" (what am I speaking, arabic?) at least in my experience.
Of course historically "turk" and "arab" were synonyms due to the fall of of Constantinople and the "contacts" with the Ottoman Empire.
And now, risking to quote myself, evidence of the sentence (by a greek) "it's English to me":
http://www.treccani.it/vocabolario/ricerca/Parlare-turco/
A more "neutral" Italian would be "Parlo forse turco?".
Curiously, it is a sentence used in literature by Andrea Camilleri which should mean that the form is also in use in Sicily.
JFYI ;-) Mario Vigorone [1980]:
BTW, I agree with the other comment that this is more common in the north.
When someone makes mistakes in English we say they speak English like a Spanish cow.