I don't know of a specific reference or origin for this expression so maybe somebody else can do better, but it just means that Bertie will be in a good mood and raring to go. To me it calls to mind a milk maid or someone skipping through the Alps and about to burst into song a la Julie Andrews in the opening of The Sound of Music. The braid specifically implies an outdoorsy sportiness. A lady's long hair might be done up in a braid if she were going to be doing something active; tennis, or skipping through the Alps with a milk pail.
Those are just my impressions though. I'd like to know if anybody has something more concrete.
no subject
Those are just my impressions though. I'd like to know if anybody has something more concrete.