The family began as the Oldbuck clan, who named themselves such apparently after Bucca of the Marish, who became the first Thain of the Shire. Ten Oldbuck Thains followed, until Gorhendad Oldbuck, the eleventh Thain, crossed into Buckland over the river Brandywine, passing the Thainship to the Took clan.
The Brandybucks formed a powerful dynasty, which became mostly independent of the Shire, although Buckland remained nominally a part of it. They were seen as 'odd folk' by the other Hobbits of the Shire because they locked their doors at night (because of the exposure to the Old Forest). It should also be noted that the Brandybucks were not only the most wary hobbit clan, but also one of the most organized in matters of militia. After the Ringwraiths invaded Frodo's house in Buckland, the militia was roused with the Horn-cry of Buckland and the militia of Buckland arrived, though the Ringwraiths escaped by riding through the Buckland Gate. This proves that the Brandybucks were not idle in matters of defense, perhaps due to their proximity to the Old Forest, and the attack of the White Wolves over the frozen Brandywine River, two instances in which the Brandybucks were capable of fending off the rare (though comparitively minor) dangers that threatened the Shire.
Masters of Buckland
The head of the family was the Master of Buckland, one of the officials of the Shire, of whom the first was Gorhendad Brandybuck. Like the Thain and Warden of Westmarch, the Master had only nominal authority. It extended across the Brandywine to the Marish of the Eastfarthing, due to the close proximity and amount of business between the two areas.
Line of Brandybucks