From the experts:
Could Hal be the Jack, Max, or Gus of the future? It just might happen in the new nickname environment. Hank Azaria put it on his son's birth certificate.
Hal is a venerable nickname for Henry, Harry and Harold, famously used by Shakespeare in King Henry IV as the name of the king's son, the future Henry V.
A number of show biz figures of a certain era have gone by the name, including Hals Roach, Wallis, Ashby, Holbrook, David and Linden. In the eponymous film, Jack Black played "Shallow Hal."
As for the bad-guy machine in "2001: A Space Odyssey," that HAL stood for Heuristically programmed ALgorithmic computer.