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If somebody can explain the meaning of : " To fly over/into the cuckoo's nest." I've read somwhere long ago that cuckoos don't make their own nests. How come this idiom/saying.
Technically speaking, the book took its title from a children's rhyme/finger game:
Wire, Brier, Limber Lock
Three Geese in a Flock
One Flew East
One Flew West
And one flew over the cuckoos nest!
O-U-T spells out
Goose swoops down and plucks you out!
But "cuckoo's nest" is often used as a (not necessarily politically correct) synonym for a mental hospital.
cuckoo's nest 
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