In Stephen King’s novel 11/22/63, the portal that sends Jake Epping into the past is called The Rabbit Hole.
Jake learns about the portal from Al Templeton, the owner of a diner in Lisbon Falls, Maine. Each trip through it leads to September 9, 1958, regardless of when the traveler enters. The portal therefore gives Jake a fixed starting point for his attempt to prevent the assassination of John F. Kennedy.
The Rabbit Hole resets when someone returns to the present, meaning changes made in the past do not remain permanently fixed until the traveler accepts the consequences. This unusual time-travel rule drives much of the novel’s plot.
The phrase echoes Lewis Carroll’s Alice’s Adventures in Wonderland, where Alice enters another world by following a rabbit. The portal is sometimes confused with a generic time machine, but King presents it as a mysterious doorway with its own rules rather than a mechanical device.