Recorded in many spellings from Brown, Broune, and De Bruyn, to Brauner, Bruni and Brunet, this ancient and prolific surname derives from a pre 7th century Germanic and Anglo-Saxon word "brun" or the Olde Norse personal name "Bruni". Originally this name would probably have been a nationlistic or tribal nickname for a person with a brown complexion or hair, although it may also have referred to someone who habitually wore brown clothing, such as a monk or cleric. The baptismal name as Brun or the latinized Brunus, was a popular name in the period upto the introduction of surnames in the 12th century, see below. Irish name holders derive from 12th century Norman sources. In the west the Browne's are the descendants of a knight called " Hugo le Brun", and form one of the ancient "Tribes of Galway", as recorded in the "Annals of the nine kings". The Browne's of Killarney form a separate branch and are descended from a later Elizabethan settler. Amongst the early surname recordings are those of Hugh Bron of Stafford, England, in the year 1274, and Hugo Brun of Erfurt, Germany, in 1407. Christopher Browne is recorded as being one of the very first settlers in the new American colonies. In the very first listing of the colonists of New England he is shown to be "living in Virginea, on February 16th 1623". The first recorded spelling of the family name anywhere in the world is probably that of William le Brun, which was dated 1169, in the Pipe Rolls of the county of Northumberland, England. This was during the reign of King Henry II, known as "The church builder", 1154 - 1189.
And of course, http://en.wikipedia.org/wiki/Brown_(surname)