What is "billycocks"

Usage examples of "billycocks".

If Cecil Rhodes's vision could come true (which fortunately is increasingly improbable), such countries as Persia or Arabia would simply be filled with ugly and vulgar fatalists in billycocks, instead of with graceful and dignified fatalists in turbans.

Maybe she had in fact bought a hat, for in her more seductive moods, she liked the glamour of berets and billycocks, panamas and turbans, cloches and calashes.