I know it's a long shot but maybe that was his name.
A friend of mine took in a little black dog and after trying, unsuccessfully, to find his owner, decided to keep him.
He was lying in his bed asleep when she was discussing with her husband what to call him, he looked at his black coat and half joking said, "suppose it will have to be Jet" the little dog jumped up and came running over.
Suppose Jet is a common name for a black dog but it was either really his name or her just liked it. HaHa.