I heard a story about the title of that song, don't know for sure if it's true but it kind of makes sense.
The song was originally titled "In The Garden of Eden" (Life) and they were to perform it on the Ed Sullivan Show.
The producers or maybe even Ed himself made them change the words as they didn't think it was acceptable.
Maybe someone here can add to this.
Same story I've always heard about that song.
I'm thinking up some more good ones:)
FWIW, here’s what Wiki says.
http://en.wikipedia.org/wiki/In-A-Gadda-Da-Vida
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 became intoxicated and slurred the words, creating the mondegreen that stuck as the title. However, the liner notes on ‘the best of’ CD compilation state that drummer Ron Bushy was listening to the track through headphones, and couldn’t clearly distinguish what Doug Ingle answered when Ron asked him for the title of the song (which was originally “In-the-Garden-of-Eden”). An alternate explanation, as given in the liner notes of the 1995 re-release of the In-A-Gadda-Da-Vida album, is that Ingle was drunk and/or high 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.