In southern Arabia live several groups, most famously the Mehri tribe, whose languages, though Semitic, are only distantly related to Arabic, and quite incomprehensible to other Arabs. (You can hear recordings of it at SemArch.) Recently I borrowed a copy of the recently published Mehri Language of Oman, by Aaron Rubin; looking through it, I could see several points where Mehri resembles Berber but not Arabic that a traveller might seize on, notably:
- -s ـس "her", -sən ـسن "their (f.)"; compare Siwi -nn-əs ـنّس "his/her", -n-sən ـنسن "their (m/f)". A 3rd person in -s was found in proto-Semitic, as shown by Akkadian, but was replaced in Arabic.
- əl ال "not" (preverbal first element of negative); compare Tumzabt ul أُل. Again, this is found in Akkadian and hence must be proto-Semitic.
- -ət ـت feminine singular; compare Siwi -ət ـت (feminine singular in Arabic borrowings.) Again, the connection is real, but dates back to proto-Semitic rather than indicating any special relationship between the two.
- -tən ـتن feminine plural; compare Berber -tən ـتن (plural of some masculine nouns)
- a- أَ used as a definite article for some nouns; compare Berber a- أَ(masculine singular noun prefix). A striking case is Mehri a-məsge:d أَمسجيد vs. Siwi a-məzdəg أمزدج "the mosque". However, in Mehri this indicates definiteness, and does not depend on gender; this is probably a coincidence.
- tə-...-əm تـ...ـم second person plural imperfective, eg təkə́tbəm تكتبم "you (pl.) write"; compare Berber t-...-m تـ...ـم. The t- is cognate; not sure about the history of the -m offhand.
- 'ār آر "except, but"; compare Tuareg ar.
- ā آ "oh" (vocative); compare pan-Berber a أ. (This is actually found in Classical Arabic as well, أ, but is not widely used.)