flappers and galoshes

[Sam Clements]

There is an oft-repeated story about "flapper" coming from the fashion in
Britain in or around WWI of young women wearing their boots/shoes unlaced or
untied, probably as a form of rebellion to convention or authority.

Assuming there was NO such fashion documented, when and where did this story
arise?

Flapper obviously goes back into the late 1800's, and morphed into what we
today think of as the classic flapper of the 1920's.  But where did that
crazy story come from?  Or is it crazy?