Kehl is the name of a Tleilaxu secret council.
Spelled as both khel and kehl in Heretics of Dune.
As it appears to be used in the Dune Universe it's possibly a council made up of the inner most clan of Tleilaxu Masters and or only made up of the Masheikh.
Probably from the Pashtun word meaning "followers of". The word is a common final element in the names of clans, tribes or villiages.
Khel (Pashto: خیل)
The Pashtuns are the world's largest (patriarchal) segmentary lineage ethnic group.
The Pashtun people are an Eastern Iranian ethno-linguistic group with populations primarily in Afghanistan and the North West Frontier Province of Pakistan. For over 300 years, they reigned as the dominant ethnic group in Afghanistan with nearly every ruler being a Pashtun and are also an important community in Pakistan, where they have attained the presidency, high positions in the military, and are the second-largest ethnic group.