Bobble hat

A knit cap, originally of wool (though now often of synthetic fibers) is designed to provide warmth in cold weather. Typically, the knit cap is of simple, tapering constructions, though many variants exist. Historically, the wool knit cap was an extremely common form of headgear for seamen, fishers, hunters and others spending their working day outdoors from the 18th century and forward, and is still commonly used for this purpose in Scandinavia and other cold regions of the world. Being found all over the world where climate demands a warm hat, the knit cap can be found under a multitude of local names.

Most knit caps are tapered at the top. The stretch of the knitting itself hugs the head, keeping the cap secure. They are sometimes topped with a pom-pom or loose tassels. Knit caps may have a folded brim, or none, and may be worn tightly fitting the head or loose on top. A South American tradition from the Andes Mountains is for the cap to have ear flaps, with strings for tying under the chin. A special type of cap called a balaclava folds down over the head with openings for just the face or for the eyes or mouth only.

Some modern variants are constructed as a parallel sided tube, with a draw-string closure at one end. This version can be worn as a neck-warmer with the draw-string loose and open, or as a hat with the draw-string pulled tight and closed.

The pull-down knit cap was known in the army of the British Empire as an Uhlan cap or a Templar cap. During the Crimean War, handmade pull-down caps were sent over to the British troops to help protect them from the bitter cold weather before or after the battle of Balaclava. The cap became popularly known a Balaclava helmet or just balaclava among the soldiers.

In Scandinavia, caps resembling a typical knit cap with a pom-pom has been in use since the Viking period and possibly earlier. The term (Danish tophue, Norwegian topplue, Swedish toppluva) means "top cap", and refers to the pom-pom. The Rällinge statuette, depicting Viking fertility god Freyr shows him wearing a pointed cap with pom-pom.

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Wikipedia