Bawn

A bawn is the defensive wall surrounding an Irish tower house. It is the anglicised version of the Irish word bábhún (sometimes spelt badhún), possibly meaning "cattle-stronghold" or "cattle-enclosure". The Irish word for "cow" is bó and its plural is ba. The Irish word for "stronghold, enclosure" is dún, whose possessive case is dhún, in this case rendering the d silent.

The original purpose of bawns was to protect cattle from attack. They included trenches that were often strengthened with stakes or hedges. Over time, these were gradually replaced by walls. The name then began to be used for the walls that were built around tower houses.

...
Wikipedia