Down the Rabbit Hole

Kind of talking off the top of my head here, while the coffee brews…

I’m assuming that your splinter group of terrorists all firmly believe that they are the only ones following the true path, with lots of references to the very earliest days of Islam when a tiny group of true believers won miraculous victories against overwhelming odds, etc. So then, they would likely take a name that invokes those early Islamic times; and as you say, likely in a snippet of badly understood, formulaic Arabic. Or, perhaps, some of the wilder apocalyptic beliefs instead. So, some ideas (all transliterated as an actual Arabic speaker would pronounce them, with the correct not necessarily like a Somali would):

The earliest kulafa’ (caliphs, successors to Mohammed) are remembered (by the Sunnis) as the “rightly guided”, or “ar rashidoon” (“al kulafa’ ar rashidoon”). “Rasheed” (singular) also means “mature”, “complete” and “perfect”, BTW. So, we could hypothesize a name like “Soldiers of the Rashidoon” (“Junood ar rashideen”), “Partisans/supporters of the Rashidoon” (“Ansar ar rashideen”), or “Army of the Rashidoon” (“Zhaysh ar rashideen”). You can google translate any other noun you’d like, of course (“Sword of the Rashidoon”, “People of the Rashidoon”, etc.) or use a Swahili word instead “Jeshi la rashidoon”, etc.

You might also focus on the concept of the hejira, where Muhammad and a small group of followers fled Mecca to Yathrib (now called “medina”, the city [of the prophet]). The first tribe to pledge loyalty to Mohammad was the “Banu Aws”, and the second was “Banu Khazraj”. Mohammad went to Yathrib to mediate a dispute between the two tribes, ultimately solving the fighting by declaring both to be Muslims and thus bloodshed between them was banned. The two banded together (as the “Banu Qayla”, a sort of tribal confederation), to then attack the dominant (Jewish) tribes in the area, in which they were extremely successful. Notably, they conquered the “Banu Qurayza”, then executed all the men and reduced the women and children to slavery and concubinage for “tribal treachery”. This is, obviously, one of the roots of modern Arab/Muslim anti-semitism… if you want to go there in your work.

Alternately, you could build off of “Yajuj wa Majuj”, the Islamic names for “Gog and Magog”, that is, a savage and vicious horde which is to fight against the believers of the world at armageddon. There’s also the “Masih ad dajjal”, the anti-Christ (lit. the most-deceiving messiah), legendarily a man with one blind and bulging eye who leads the world astray into materialism, apostasy, and various calamities. Islamic apocalypse legends, like everyone else’s apocalypse legends, get weedy and weird pretty quick; you can just google for some inspiration, then let your imagination go– there’s no worry about being actually accurate, as people pretty much just make these up out of whatever fever dream they just had.

If you want something more specifically spirit-related, there are a number of named angels/demons in both the Quran and the Hadeeth. Some you might be interested in are:
Azrael: the angel of death
Iblis: Lucifer, head of the evil demons
Maalik: Angel who guards Hell
Ridwan: Angel who guards/runs Heaven
Darda’il: angels sent to seek out and test people’s faith in God
Mu’aqqibat: guardian angels, who protect the faithful against death before the appointed time
Kiramaan Katibin: (lit. the two honorable scribes) two angels who record everything good and bad that an individual does

Hope that gets your juices going, if nothing else.

Janet