The modern four-string violin is generally considered to have originated about 1550 in northern Italy. The earliest violins incorporated features of existing bowed instruments: the rebec, the Renaissance fiddle, and the lira da braccio. The pear-shaped rebec had strings that were tuned in fifths, and this system was adopted for the violin. However, the shape of the violin was taken from the fiddle and the lira da braccio, as these larger instruments produced a bigger sound, and the hourglass shape made bowing easier.
The violin was initially used for vocal and dance accompaniment, while its cousin, the viola da gamba, remained the preferred bowed string instrument for ensembles. By the seventeenth century, composers like Monteverdi began to incorporate violins into instrumental ensembles, where they eventually replaced the viola da gamba.
Arkenberg, Rebecca. “Renaissance Violins.” In Heilbrunn Timeline of Art History. New York: The Metropolitan Museum of Art, 2000–. http://www.metmuseum.org/toah/hd/renv/hd_renv.htm (October 2002)