ODO's definition for bottle includes the following:
2 [mass noun] British informal the courage or confidence needed to do something difficult or dangerous:
I lost my bottle completely and ran
British informal lose one’s nerve and decide not to do something:
the Minister has bottled out of real reforms
Where does this use of the word bottle come from? Both the examples in the ODO definition are negative in connotation; are there positive ones too? Can someone have the bottle to do something?