Bally is the anglicised version of the Irish word baile. The baile, also known as the baile biataig or ballybetagh, in the north, was the basic property unit of the Irish lineage group or sept in the medieval period. A baile could range in size from c.700 to c.7,000 acres depending on the size of the sept and the part of the country in which it was located. Each baile included a mix of pasture, arable, turbary land, etc. and acted as an independent economic entity. Most baile were held by family heads as freeholders or were held by hereditary office families. The baile was also the unit in which property was periodically redistributed between sub-family groups. The baile was normally divided into four quarters and these were also quartered to form sixteen parts. A group of baile formed a trícha cét or local kingdom under a sub-king.
Paul MacCotter 2008. Medieval Ireland. Territorial, political and economic divisions. Dublin.