House Fenring was a House Major during the days of the Faufreluches. Its head was usually a Count, and it was close to the Imperial House.
A known head of House Fenring was Count Hasimir Fenring. He was an assassin, as well as friend and confidant to the Padishah Emperor Shaddam IV. Dalak Fenring was another notable member of the house, as well as Count Otho Fenring, who was Imperial representative who worked on the final draft of the Assassins' Handbook in 5359 AG.
This Major House never had a secure Homeworld, though was usually situated near House Corrino. It ruled Arrakis for sometime, then Count Fenring became Siridar-Absentia of Caladan. At the beginning of the reign of Emperor Paul Atreides, House Fenring had 2 votes in the Landsraad.
Sources: Dune Encyclopedia?,