The planet Pluto is named after Pluto, the god of the underworld in Greek and Roman mythology. The name was suggested by a young girl, Venetia Burney Phair, in 1930 when she heard the news that a new planet had been discovered in the solar system.
Venetia was familiar with Greek and Roman mythology as well as the names of the planets. Since Pluto had not been used yet, she made the suggestion to her grandfather, a retired Oxford University librarian. Her grandfather passed on the idea to an Oxford astronomer who relayed it to colleagues at a conference. The name Pluto was chosen for the new planet in May 1930.