Coo coo ka choo

I have heard this saying on a few songs I do not know its meaning. For instance Mrs. Robinson a song by Simon and Garfunkle uses the term coo coo ka choo Mrs Robinson any onfo would be appreciated. Thanks
Pattie

Also in a Beatle's song--The Walrus:
"...Expert, texpert
Smoking choker
Dont you think the joker laughs at you..."
"...I am the walrus-- coo coo ka choo"

Just my opinion but I don't think "coo coo ka choo" has a meaning---sounds like just nonsense syllables like "doo wop doo wop" or "shad a lack a jingle bop", "rama lama ding dong" and "boogity boogity shoo".