Developed from the earlier blue bonnet, dating to at least the 16th century, it takes the form of a knitted, soft wool cap with a flat crown.
Originally with a voluminous crown, today, the bonnet is smaller, made of finer cloth, and tends to be dark blue, black, or Lovat green.
[citation needed] As worn by Scottish Highland regiments, the blue bonnet (common civilian headwear) gradually developed into two military forms.
A mid-18th-century portrait of Lord George Murray shows a black cap essentially indistinguishable from a Balmoral, but sometimes described as a "blue bonnet".
Balmorals were described in 1842 as having become common civilian headwear "worn pretty generally by ploughmen, carters and boys of the humbler ranks".