House Ginaz

House Ginaz was a Great House of the Landsraad during the time of the Faufreluches. It was an ally of House Atreides during the time of Duke Leto the Just. They were defeated in a War of Assassins by House Moritani of planet Grumman.

Swordmasters of Ginaz
House Ginaz was renowned throughout the Imperium for its Swordmaster School. Presumably, many Great Houses would send a gifted soldier to be trained at this school. It was said that to reach the Ginaz School Tenth Level was to be a superior warrior in every way, even more adept than Imperial Sardaukar.

Anyone who graduated from the Ginaz School was awarded the title Swordmaster of the Ginaz. During the time of Leto I, the Atreides maintained their own Swordmaster in the form of Duncan Idaho. Swordmasters were more than mere soldiers and often functioned as chief tacticians, military advisors, and even tutors to the Houses whom they served.

Other Versions
According to The Dune Encyclopedia, House Ginaz was descended from a troop of traveling entertainers led by one Alberto Ginaztera which had risen to minor nobility.

In Prelude to Dune, House Ginaz does not exist. The Swordmasters are still based on planet Ginaz but are governed by a council of veterans and follow an idiosyncratic religion, the Ginaz-beliefs.