the arabic word for them, FALAJ (and its plural AFLAJ) are also useful scrabble words (lowish probability, but very useful when you do have them playable)
https://en.wikipedia.org/wiki/Broken_plural
Look a few rows into the patterns table, and you start seeing fun rearrangements for patterns such as CaCaC -> ʼaCCāC, the example being sabab -> ʼasbāb.
Pretty fascinating stuff!