Rupert's Hole; what's in a name?

Why would this planet get named Rupert's Hole? I don't remember ever hearing of another sci Fi location named in a similar manner. We can presume that Cassidine was discovered and explored about the time the vrusk, dralasites and humans met and that this led to the naming of Triad as the first multi species colony designed to promote exchange, learning and understanding. But why add the word hole to Rupert's planet?