The RCAHMS record describes this site as a Bronze Age cairn about 1m high. Although the Denham Tracts mentions the following folklore in relation to 'Pyper Knowes' (as here ) I think the mention of Greenlaw parish must put it here as all the other stories are local, and any Pipers Knowes are a long way off, and knowing of other dodgy spelling examples...
"[The fairies] used to come out from an opening in the side of the knowe, all beautifully clad in green, and a piper plaing to them in the most enchanting strains." They once attempted, but failed, to abstract the shepher's wife of little Billy when in childbed; and they were detected loosening Langton House from its foundations in order to set it down in an extensive morass called Dogden Moss, in the parish of Greenlaw, but were scared by the utterance of the holy name.*
*Henderston's Popular Rhymes of Berwickshire.
From volume 2 of the Folklore Society's publishing of the Denham Tracts (1895).