As noted for another feature, eski (from French est-ce que) began to be used since the recent past (1960s or 1970s?). Since it does not occur in Taber (1965), it must not have been in my corpus, but it is also absent in Bouquiaux (1978). It does occur in Diki-Kidiri (1998). The interrogative contour is not used when the sentence has a question word in other kinds of questions.
Source: nd
Source: nd