A flat cap is a rounded cap with a small stiff brim in front. The hat is also known as a cabbie cap, longshoreman's cap, cloth cap, scally cap, Wigens cap, ivy cap, derby hat, jeff cap, duffer cap, duckbill cap, driving cap, bicycle cap, Irish cap, Newsboy cap, Crook cap, Joao's hat, Sixpence, or a Paddy cap and in regional varieties: in Scotland as a bunnet, in Wales as a Dai cap, and in New Zealand, as a cheese-cutter. Cloths used to make the cap include wool, tweed (most common), and cotton. Less common materials may include leather, linen or corduroy. The inside of the cap is commonly lined for comfort and warmth.
The style can be traced back to the 14th century in Northern England, when it was more likely to be called a "bonnet", which term was replaced by "cap" before about 1700, except in Scotland, where it continues to be referred to as a "bunnet".
A 1571 Act of Parliament to stimulate domestic wool consumption and general trade decreed that on Sundays and holidays, all males over 6 years of age, except for the nobility and "persons of degree", were to wear woollen caps on pain of a fine of three farthings (3/4 penny) per day. The Bill was not repealed until 1597, though by this time, the flat cap had become firmly entrenched as a recognised mark of a non-noble subject, such as a burgher, a tradesman or an apprentice. The style may have been the same as the Tudor bonnet still used in some styles of academic dress.
In the 19th and early 20th centuries, when men predominantly wore some form of headgear, flat caps were commonly worn throughout Britain and Ireland. Versions in finer cloth were also considered to be suitable casual countryside wear for upper-class English men. Flat caps were worn by fashionable young men in the 1920s. Boys of all classes in the United Kingdom wore flat caps during this period.
In the United States the caps were worn from the 1890s. The cap grew in popularity at the turn of the 20th century and was at the time standard boys' wear. They were worn to school, for casual wear, and with suits. Flat caps were almost always worn with knicker suits in the 1910s and 20s. Both flat caps and knickerbockers declined in popularity during the 1930s. The flat cap made its way to southern Italy in the late 1800s, likely brought by British servicemen. In Turkey, the flat cap became the main headgear for men after it became a replacement for the fez, which was banned by Mustafa Kemal Atatürk in 1925.