There are parts of the UK where the normal pronunciation of book is not the short book that rhymes with hook, but is rather the long booook.

Lancashire is one such place (although with three, rather than four "o"s ) and chook is pronounce herealmost like "chuck". Whilst not everyday parlance, it is not infrequently used as a mild term of endearment.

In Northamptonshire (and Leicestershire, which is next door) the most common expression - used by all to all, regardless of sex - is "My duck." (pronounce "me dook" - rhymes with book)
Why are fowl seen as an apt metaphor for friendly humans? Most of the fowl I've come across are just that!
(perhaps there is a sociological eggquation to explain it )