In-A-Gadda-Da-Vida Video (MV)

A commonly related story says that the song's title was originally "In the Garden of Eden", but at one point in the course of rehearsing and recording, singer Doug Ingle got drunk and slurred the words. However, the liner notes on 'the best of' CD compilation state that drummer Ron Bushy was listening to the track through headphones, and could not clearly distinguish what Ingle said when he asked him for the song's title.

An alternative explanation given in the liner notes of the 1995 re-release of the In-A-Gadda-Da-Vida album, is that Ingle was drunk, high, or both, when he first told Bushy the title, and Bushy wrote it down. Bushy then showed Ingle what he had written, and the slurred title stuck.
-Wikipedia