According to Arab traditions, tribes are divided into different divisions called Arab skulls (جماجم العرب), which is a term given to a group of tribes of the Arabian Peninsula, which are described in the traditional custom of strength, abundance, victory, and honor. A number of them branched out, which later became independent tribes (sub-tribes). And the reason why they are called skulls is that the skull is the most important part of the body and every Arab tribe is a descendant from these major tribes.