The surname Jones is a patronymic name meaning "son of John (God has favored or gift of God)."
The forename Johannes was borrowed in the Roman period and became
Ieuan in Welsh. This is pronounced something like Y-eye-an. When permanent surnames were adopted in Wales, Ieuan sometimes became Jones and sometimes Evans. A document of 1533 names Thomas ap Ieuan ap David ap Blethyn alias Thomas Jones. In the mediaeval period, John was borrowed and in time this became used as a surname, sometimes unchanged, sometimes in the style Jones. The forename John is known to have been used in Wales in the thirteenth century.
http://genealogy.about.com/library/s...name-JONES.htm
http://www.data-wales.co.uk/jones.htm
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