A bonnet is any of a wide variety of headgear for both sexes—more often female—from the Middle Ages to the present. It is impossible to generalize as to the styles for which the word has been used any more than for the hat and cap, but there is for both sexes a tendency to use the word for styles in soft material and lacking a brim. Yet the term has also been used, for example, for steel helmets. This was from Scotland (in 1505), where the term has long been especially popular. Bonnet derives from the same word in French, where it originally indicated a type of material. In the 21st century, only a few kinds of headgear are still called bonnets, most commonly those worn by babies and Scottish soldiers. In addition, bonnets are worn by women as a Christian headcovering in some denominations.
The most common kind of bonnet worn today is a soft headcovering for babies. Its shape is similar to that of some kinds of bonnets that women used to wear: it covers the hair and ears, but not the forehead.
In the mid-17th and 18th century house bonnets worn by women and girls were generally brimless headcoverings which were secured by tying under the chin, and which covered no part of the forehead. They were worn indoors, to keep the hair tidy, and outdoors, to keep dust out of the hair. With hairstyles becoming increasingly elaborate after 1770, the calash was worn outdoors to protect the hair from wind and weather: a hood of silk stiffened with whalebone or arched cane battens, collapsible like a fan or the calash top of a carriage, they were fitted with ribbons to allow them to be held secure in a gale.
From Waterloo, more structured fashionable bonnets made by milliners rapidly grew larger. A plate in La Belle Assemblée 1817 showed a
Bonnet of vermillion-coloured satin, embossed with straw, ornamented slightly with straw-coloured ribbands, and surmounted by a bouquet formed of a full blown damask rose and buds, with ears of ripe corn. This ornament is partially placed on one side: the edge of the bonnet finished by blond [lace] laid on strait.
This was specified as a carriage dress, with the understanding that when taking the air in an open carriage, the bonnet provided some privacy—such a bonnet was in fact an invisible in Paris—and prevent wind-chapping, with its connotations of countrified rude health. Straw was available again after 1815: the best straw bonnets came from Leghorn. As a bonnet developed a peak, it would extend from the entire front of the bonnet, from the chin over the forehead and down the other side of the face. Some styles of bonnets between ca 1817 and 1845 had a large peak which effectively prevented women from looking right or left without turning their heads: a "coal-scuttle" or "poke" bonnet. Others had a wide peak which was angled out to frame the face. In the 1840s it might be crimped at the top to frame the face in a heart shape. As the bonnet became more complicated, under it might be worn a lace cornette to hold the hair in place.
Bonnets remained one of the most common types of headgear worn by women throughout most of the 19th century. For a widow, a bonnet was de rigueur. Silk bonnets, elaborately pleated and ruched, were worn outdoors, or in public places like shops, galleries, churches, and during visits to acquaintances. The idea was that women would cover their heads with caps out of modesty as prompted by Biblical customs of ancient times. In addition, women in wedlock would wear caps and bonnets during the day. 
Under the French Second Empire, parasols took the place of protection from sun, and bonnets became smaller and smaller, until they could only be held on the head with hatpins. As hats came back into style, bonnets were increasingly worn by women who wanted to appear modest in public, with the result that bonnets accumulated connotations of dowager wear and dropped from fashion except on the prairies.
Most middle-class women in the 19th century would have had at least two bonnets, one suitable for summer weather, often made from straw, and one made from heavier fabric for winter wear. This is where the tradition of an Easter bonnet originated, when women would switch from their winter bonnet to their summer bonnet. Wealthier women would have many bonnets, suitable for different occasions.
Women of some religious groups have continued to wear bonnets for worship or everyday clothing. This is especially the case among plain people, such as plain-dressing Friends (Quakers), Old Order Mennonites and the Amish. Bonnets were adopted by the Salvation Army as part of uniform regalia for women. Initially, Salvation Army bonnets were introduced as protection for women soldiers and were reinforced with black tar to turn them into helmets. Later versions were smaller when there was no longer any need for protection. The bonnet has now been replaced with a bowler hat.
In France, single women wear elaborate yellow and green bonnets to honor St. Catherine's Day on November 25. The French expression coiffer Sainte-Catherine ('don St. Catherine's bonnet'), an idiom that describes an unmarried woman of 25 years or older, derives from this custom.
The word bonnet for male headgear was generally replaced in English by cap before 1700, except in Scotland, where it remained in use, originally for the widely worn blue bonnet, and now especially for military headgear, like the feather bonnet (not to be confused with those worn by Native Americans, for which bonnet was also used), Glengarry, Kilmarnock and Balmoral. The Tudor bonnet remains a term for a component of the academic regalia of some universities, and is not unlike the common male bonnet of the 16th century.
Bonnet is also the term for the puffy velvet fabric inside the coronet of some male ranks of nobility, and "the affair of the bonnets" was a furious controversy in the France of Louis XIV over the mutual courtesies due between the magistrates of the Parlement de Paris and the Dukes of France.
The Scotch bonnet pepper was named for its resemblance to a bonnet worn by men in Scotland in the past, as it had a pom pom at the top which indicates the difference form the men's bonnet and women's bonnet.
Various tam o' shanters
- OED, "Bonnet"
- Bercot, David (2017). "Head Covering Through the Centuries". Scroll Publishing. Retrieved 11 May 2017.
- Wass, Ann, and Michelle Fandrich. Clothing through American History: The Federal Era through Antebellum, 1786-1860. Library of Congress Cataloging-in-Publication Data, 2010.
- Bender, Harold S. and Sam Steiner. "Bonnet (1953) Archived December 12, 2007, at the Wayback Machine.." Global Anabaptist Mennonite Encyclopedia Online. 2000. Global Anabaptist Mennonite Encyclopedia Online. Retrieved 2007-04-27.
- "Coiffer sainte Catherine". La France pittoresque (in French). November 24, 2016.
- OED, "Bonnet" 4
|Wikimedia Commons has media related to Bonnets.|
|Look up bonnet in Wiktionary, the free dictionary.|