Sui generis
In sociology, the "sui generis" is what has been externalized, then internalized in the overall public and becomes a part of society that simply exists in its construct. It is not something that is not thought to have been created, because it is imbedded in everyone's way of thinking and being. Instances include the idea of love, or going to school, or clothing belonging to a specific gender. These examples are "sui generis" for they simply exist in society and are widely accepted without thoughts of where they come from or how they were created.
History of Sussex
Borough-English was the custom that lands should descend to the youngest son or daughter, or, in default of issue, to the youngest brother of the deceased. The name originated from a case in Nottingham in 1327 when the English borough, or part of the town, held to ultimogeniture, the French (Norman) part to primogeniture. In Sussex, inheritance by Borough-English, could still be found on 134 manors after 1750.