What was Columbo's first name in the show 'Columbo'?

Columbo’s First Name and The Supreme Court - The “Philip Columbo” Story
Columbo’s first name was the subject of a $300 million lawsuit, in the 1980s, that was appealed all the way to the Supreme Court of the United States. Fred L. Worth, a former air traffic controller from Sacramento, California, wrote a book called “The Trivia Encyclopedia”, published in 1974. The book was followed by “The Complete Unabridged Super Trivia Encyclopedia” in 1977, a big success which led to additional “Super Trivia” books including “Super Trivia, vol. II” in 1981. Fred was convinced that trivia was about to become a boom industry, and he wanted to protect the work that he had assembled. However, he realized that no one can “own” facts of public record – he could only try to claim rights to the form of his own compilation. In “Super Trivia”, Fred had included the statement that Columbo’s first name was “Philip”. This assertion was completely invented by Fred, for no purpose except to trap potential copycats.