Cefn Du is noted in the rentals list of the Baron Hill in 1707 (archive reference Baron Hill 4742) and the rentals list for the Henllys estate in 1751 (reference Henllys 1164).
It was noted by a local resident that Cefn Du previously came under the Carreglwyd estate, and the relevant information is below.
As shown, work took place at ‘Cefn dy’ for the Rev. Mr Holland on March the 6th 1739, and Wages and costs incurred by the erection of a cow house at ‘Cefn Du’ for Mr Holland in November 1739. Although Cefn Du has a different spelling in the first instance, we can assume both refer to the same Cefn Du.