The Sisk system was a star system located in the Calaron sector of the Outer Rim Territories. It contained the planet Sisk, homeworld of the Sic-Six species.
Sources[]
"Twinkle, Twinkle Little Star, How I Wonder Where We Are" — Voyages SF 13 (Unlicensed)
Star Wars: The Essential Atlas Online Companion on StarWars.com (article) (backup link) (First mentioned)