The آل in Arab family and tribal names

We have all heard of the well known Arab families, such as آل سعود‎ (Al Saud), آل صباح‎ (Al Sabah), آل ثاني (Al Thani), آل رشيد (Al Rasheed), etc. The word آل came from either the جذر أ و ل  , which has to do with family or people, or from the word أهل , from جذر أ ه ل , which also has to do with family or people.

آل البيت could refer to the blood relatives and descendants of محمد
أهل البيت could refer to all Muslims collectively or to the family of محمد

Some Arab tribes have names like آلبو صالح (Albu Salih) or آلبو نمر (Albu Nimr). The آلبو is a shortening of آل أبو . So آلبو نمر is really آل أبو نمر , The Descendants of The Father of Nimr, or the Abu Nimr Tribe. But the people just say آلبو نمر , and so we write Albu Nimr.