The bowler and the derby are simply two names for the same style of hat. Bowler hats began to be called derby hats after an American hatter noticed a large number of English gentleman sporting them at an English derby (derbies are races typically restricted to three year old horses and were popular in 19th century England).
Naming the Bowler
In 1850, the hatters James and George Lock of Lock's of St. James Street designed the now famous bowler hat. The Locks named their design the "Coke" in honor of the hat's commissioner, Thomas William Coke the 2nd Earl of Leicester. When the Locks sent their design to the London hatmakers Thomas and William Bowler to construct the prototype, the design, which would later become one of the most popular men's hat designs ever, became known as the bowler.
Building the Bowler
Constructed from stiff felt, the bowler was given a coat of shellac to harden the rounded crown and narrow brim. Though hatmakers exclusively made bowlers in the stiff style at first, they later offered a flexible style as well.
Putting the Bowler to Work
Bowlers were popular with gamekeepers and riders who appreciated the protection that the hat's stiff crown afforded them from low-hanging branches. Riders and those involved in active sports also considered bowlers a practical alternative to the high beaver hats that gentlemen wore on the streets of London.
Popularizing the Bowler
Because they bridged the gap between the formal top hats favored by the upper classes and the soft felt hats worn by the lower classes and because they were the first hat to be mass produced and affordably priced, bowlers quickly became popular with the middle class. In fact, US tradesmen and artisans of all classes sported bowlers throughout the 19th century. Bowlers remained a staple in men's fashion until the Fedora became popular in the 1920s.
Caring for the Bowler
Bowlers should never be handled by their crown but should instead be picked up by their brim. Ideally, bowlers should be simultaneously handled by both the front brim and the back brim. Also, dusty bowlers should be brushed using a specially designed horse-hair hat brush. To retain their shape, bowlers should be set on their sides with their weight resting on both the brim and crown.
Owning the Bowler
Many hat retailers sell inexpensive felt bowlers for around $30 while some retailers, like Christy's of London, offer more authentic fur felt bowlers for around $300.