Jason was a Sphinxian treecat.
He was one of Nimitz and Samantha's first litter. He and his siblings (Achilles, Andromeda, and Cassandra) were the first treecat kittens ever to live with humans from birth, as well as the first kittens ever to leave the planet Sphinx. James MacGuiness named him shortly after birth due to his wanderings and explorations.[1] (HH7)
His true name, Wanderer, was assigned when he was less than a T-year old as a recognition of his propensity to wander[2]. (CS4)