Unidentified swamp planet
From Wookieepedia, the Star Wars wiki.
An unknown swamp planet was the home of Jedi Master N'Kata Del Gormo. When a young Yoda and his Human friend crashed near where he was living, the Jedi Master took them in for training.
[edit] Behind the scenes
The unknown swamp planet may have been intended to be Dagobah, but George Lucas has overrode this fact by stating that Yoda had never visited Dagobah before his exile.
