In the Christian Bible (and the Tanakh?), Japheth was one of the sons of Noah. Based upon the theory that all current humans are descendants of Noah, some medieval scholars posited that the peoples of the world could be placed into one of three categories corresponding with each of Noah's sons. Examples of adherence to this theory can be seen as late as the late 19th c.; however, the huge advances made by 20th c. archaeologists, anthropologists, and ethnographers have served to place this theory in to the realm of "quaint old belief."
Pierer's Lexikon, a German-language reference book (circa 1890) states as follows : Japhet(h) ( Hebrew , meaning spread out over far distance- enlargement), was the third son of Noah. Japhet(h) is considered the father from whom descend the Medes (Medians), Armenians, Greeks, Celts, Germans, and Slavs . All these people are called Japhet(h)ites. An article in a Swiss publication Uni-Press # 104 from April 2000 is named "The Rebirth of Cartography ( Die Wiedergeburt der Kartographie) 500 years ago". It shows a reprint of a first "world map" of 1472 identifying people of the world under Noah's sons S(h)em in Asia , Ham in Africa , Japhet(h) in Europe.
Outside link : Uni-Press, Bern Switzerland: http://publicrelations.unibe.ch/unipress/heft104/beitrag10.html from booklet 104 April 2000