Berberised Afro-Latin speakers in Gafsa

One reader of my last post asked how late Latin (or some descendant thereof) continued to be spoken in North Africa. The answer is, pretty late: the latest attestation I came across on short notice seems to be in the major medieval geographer Al-Idrisi (12th century) who, describing Gafsa in southern Tunisia, notes that:

وأهلها متبربرون وأكثرهم يتكلّم باللسان اللطيني الإفريقي.
Its inhabitants are Berberised, and most of them speak the African Latin tongue.

He even gives one word of their dialect:

ولها في وسطها العين المسماة بالطرميد.
In the middle of the town is a spring called the ṭarmīd (perhaps to be related to Latin thermae).

One interesting thing to note about this statement is that he said that the town was Berberised - in other words, that, in the very century when the Banū Hilāl were rapidly spreading through Tunisia and Libya (a subject he has fairly harsh things to say about), Berber culture was prestigious enough to be adopted by members of other cultures, in particular the remaining Roman or Romanised towns, in the area. Gafsa, of course, speaks Arabic now, but several nearby villages still spoke Berber in the 1800s, and two, Sened and Majoura, well into the 1900s.