The Triumvirate was the name used by spacers for the three major Tunroth homeworlds: Jiroch-Reslia, Jiroch-Saloch and Jiroch-Kalok. The Tunroth of Jiroch-Reslia settled the other two planets when they joined the Galactic Republic around 9000 BBY.
The name was a dedication to the Assemblage of Three who promoted their colonization.