Humphrey is an old name that might have faded completely were it not for that Bogie flair. A royal name in Britain, where it's used somewhat more frequently, Humphrey might just have some life beyond Bogart here, especially with the recent interest in the names of Golden Age Hollywood stars. His first name was the maiden name of his mother, Maud Humphrey, a well-known illustrator who used baby H. as a model.
Humphrey was brought to England by the Normans and was made famous by Duke Humphrey, the fifteenth century Duke of Gloucester and youngest son of Henry IV, a noted patron of literature, who appears in Shakespeare's Henry IV. In other literature, Humphrey Wasp is a character in Ben Jonson's Bartholomew Fair, and the eponymous hero of Tobias Smollett's early novel Humphrey Clinker.
Bottom line: An interesting name with a noirish edge.