Moore has certainly made absolutely no bones about his incredible dislike (borderline hatred) of President Bush.

Where does this phrase originate from?

Thank you.

suggest first searching at
you'll find comments about this idiom

the origin is quite controversial.
some say it comes from the idea that people eat soup with no bones confidently, in a manner of speaking, they swallow it without fear of being hurt.
if you make no bones about something when you speak, you do not fear of the consequences.

 Marius Hancu's reply was promoted to an answer.