While the history of stringed instruments played by plucking has been around for thousands of years, it is believed that stringed instruments played with a bow (like the violin) have probably been around for about 1000 years. It most likely began in the horse cultures of central Asia since horse hairs from the tail were the original source of the stringed portion of the bow. The basic horse hair bow was kept the same through the centuries and ultimately utilized in Europe where it flourished in the latter part of the millennium.
Even today, the best violin bows are still made from horse hair coated with a rosin to increase the friction of the hairs and produce a better sound when drawn across the violin strings. A violin bow will contain between 150 and 200 hairs. Other instruments use different numbers of hairs per bow. Of course less expensive synthetic alternatives such as nylon are used in less expensive bows.
The wood shaft on the outer part of the bow is traditionally made from a type of wood found in Brazil called pernambuco. This type of wood is now scarce and very expensive, so other types of wood and synthetics like carbon fiber are now used. If wood is used to make the shaft, a great deal of the effort in bowmaking involves curving and shaping the wood to very exact specifications using a solvent like alcohol to soften the wood and heat to set it.
Finally, the mount that holds the hairs/strings to the shaft is called the frog. The materials used here can vary widely and often impart a decorative flair to the bow. Ebony and mother of pearl are sometimes used to this effect, and the metal used to grip the hair can be made of nickel, silver, or gold to denote the corresponding quality of the bow.