Oddly enough, however, not only language but even etymology is being used as a tool of division. As I looked through page after depressing page on the events, I was surprised to notice that, while Mzabi pages, and neutral ones, spelled Ghardaia غرداية (Ghardāyah), Chaambi pages rather consistently spelled it غارداية (Ghārdāyah). The latter spelling turns out to be based on a folk etymology, deriving the name of "Ghardaia" from Arabic ghār "cave" plus Dāyah, the name of a woman – who some Chaamba claim was from the Arab tribe of Said Atba, proving that Arabs got there before the Mzabis did (قبائل الشعانبة… بنو سُليم الجزائر.) Mzabis have a version of the same etymology, in fact (chanson amazigh mozabit) – but according to them, Daya was a saintly Ibadi woman from Touat, proving that they were there first.
Either version is problematic, since the name is pronounced ɣərdāya (Berber taɣərdayt), not ɣārdāya. The Said Atba idea is especially implausible: in 1053, when Ghardaia was reportedly founded, Ibadi Berbers had been trading across the Sahara for centuries, whereas Arab nomads had barely begun to reach the area. Phonetically, the more obvious etymology is Mzabi Berber taɣərdayt "mouse" – but who'd name a town "Mouse"? Delheure suggested a derivation from tiɣərdin "shoulders", a term found in Ouargli Berber, based on its topography (followed eg here). Dabouz compares it to a Nafusi term reportedly meaning "land next to a wadi". No proposal seems entirely satisfactory, which is itself an indicator of the placename's antiquity.
Be that as it may, this pointed use of "cave of Dāyah" reinforces my impression that what's going on is a mapping of economic grievances onto ethnic/religious categories. Adding this one letter effectively says "Mzabis own this place, but by rights it should be ours" – a thoroughly wrong attitude. الله يهديهم ويهدينا!