Fintleborxtug was a planet said to have a soft and bouncy, trampoline-like surface, once visited by the Doctor sometime before their thirteenth incarnation.
History
The founder of the planet allegedly named it while in the middle of a hiccup, and immediately before vomiting, leaving it ambiguous as to whether it was the planet's name or just the sound the founder made.
The Thirteenth Doctor claimed to have bounced there shortly after eating ice cream sundaes, which she cited as being a mistake. (PROSE: Things She Thought While Falling)