The phrase was first used in songs by artists such as The Beatles and shortly after by Simon & Garfunkel. This phrase has absolutley no definitive meaning given by dictionaries or artists such as John Lennon who first used it. The phrase has two other widely known spellings: goo goo g'joob
and coo coo ca choo
. It is believed to be used in songs and in 60s and 70s slang as a phrase left to be freely interpreted by anyone based on the surrounding context it is used in. The freedom to betsow any meaning upon the phrase makes it a statement about freedom of expression, which is a meaning in itself.
A widely accepted variation of the meaning is a slang way to assure the state of things is entirely fine; an expression of reassuring goodness.
In "That '70s Show", Donna Pinciotti said coo coo ca choo
as an end to a random string of rhymes while stoned
Man, you been a naughty boy, you let your face grow long.
I am the eggman, they are the eggmen.
I am the walrus, goo goo g'joob.
--The Beatles' "I Am The Walrus"
Hide it in a hiding place where no one ever goes
Put it in your pantry with your cupcakes
It's a little secret, just the Robinsons' affair
Most of all, you've got to hide it from the kids
Kookookachu Mrs Robinson
--Simon & Garfunkel's "Mrs. Robinson"
"Everything is all right." "No worries." "All is good."
Coo Coo Kacu is modernized for the old English Term Cuckold - which refers to a mans wife having carnal relations with another man while she is still married to him, the cuckold. Thus coco kachu - Mrs Robinson - as between Ann Bangkroft and Dustin Hoffman in the movie The Graduate
Refer to Chaucer's Canterbury Tales, The Graduat Movie with Dustin Homan - Song lyrics to the Graduate include the term Coo Coo Kachu. Maybe I am just too old but what I remember is that in the movie The Graduate, Mrs Robinson, the person the song was about was taunted with koo koo kachu Mrs Robinson referring clearly to the fact that Mr. Robinson was a cuckold. This term coming from old English and meaning that the cuckold's wife, Mrs. Robinston, was screwing another man while she was still married.
I was in college when The Graduate came out and this was discussed for at least two full class sessions. We were also dicussing Chaucers Canterbury Tales at the time where one of the main characters was also cuckold.