PAIN (PAINE):

Pain: variant of Paine.

Payne: English variant of Paine.  Irish: well-established surname.

PAINE:  English (mainly Kent and Sussex): from the Middle English personal name "Pain(e)" or "Payn(e)" (Old French "Paien," and from Latin "Paganus").  Introduced to Britain by the Norman conquerors.  The Latin name is a derivative of "pagus", (an outlying village), and meant at first a person who lived in the country (ass opposted to "urbanus" ...a city dweller).  Then the meaning advanced to a civilian, as opposed to a soldier, and eventually came to mean a heathen (one not enrolled in the army of Christ).  This remained a popular name in the Middle Ages and then died out by the 16th Century.

From: Dictionary of American Family Names, Oxford Univ Press, ISBN 0-19-508137-4. Courtesy of Ancestry.com's search tool.