"Rumbly in My Tumbly" is a song from the 1966 musical film featurette Winnie the Pooh and the Honey Tree. The song is also incorporated into the 1977 musical film, The Many Adventures of Winnie the Pooh which is an amalgamation of the first three Winnie-the-Pooh featurettes including "Honey Tree".
In the song Winnie the Pooh complains light-heartedly of a rumble in his constantly hungry and ever-growing stomach, indicating his hunger. Pooh feels compelled to feed his urge and get some honey from a honey tree.
The song was written by Robert & Richard Sherman who have written most of the music for the Winnie-the-Pooh franchise over the years.