Many believe mandolins originally evolved from the Lute family on Italian soil during the 17th and 18th centuries, and the deep-bowled mandolin produced in Naples became the most common type in the nineteenth century. The original instrument was the called a mandola (mandorla is "almond" in Italian, a refrence to the instrument's body shape) and later evolved and transitioned in the fifteenth century from the lute. As the mandola become smaller, it became known as a mandolina.
Reaching back ever farther in history, around 5,000 BC to 8,000 BC, single stringed instruments have been seen in cave paintings. They were played with a bow, or struck and plucked. From these, the families of instruments began to branch off into their somewhat primal forms of the instruments we know today. Single strings were long and gave a single melody line. In order to make the playing of the instrument more scales were shortened drastically and other strings were added with a different tensions to create different sounds. In turn, this led to being able to play diads and chords. The bowed family became the rabob, rebec and then the fiddle becoming the violin and modern family by 1520 (incidentally also in Naples). Instruments that were commonly plucked led to lute-reminiscent instruments in 2000 BC Mesopotamia, followed by appearing in Spain in 711 courtesy of the Moors.
In the following centuries frets were added and the strings doubled to courses, leading to the first full-fledged Lute appearing in the 13th century. The history of this elusive string instrument and the mandolin are deeply intertwined from this point on. The lute gained a fifth course by the 15th century and up to thirteen courses in its heyday. As early as the 14th century a miniature mandola called a mandora appeared. The name has really evolved, right? Similar to the mandola, it had counterparts in Assyria (pandura), the Arab countries (dambura), and Ukraine (kobza-bandura). From this, the mandolino, a smaller mandola with six strings tuned g b e' a' d g and sometimes called the Baroque mandolin was played with a quill and believed to be of Italian creation. The mandolino was sometimes called a mandolin in the early eighteenth century (around 1735) Naples, which is where the name we know today came into play.