The name 'Pentre Berw' is thought to either refer to a place where watercress grows, or to the waterfall that is present on the village's steep-sided rock in the rain. The English name for the village, Holland Arms, comes from the Holland family who once lived in the village. Berw and Esceifiog were termed as medieval townships. Coal was mined at Cors Ddyga.
Bell pits were sunk during the
Tudor dynasty. From 1700 onwards to 1803 the mining process evolved to deep pits 109 yards deep using large horse winding machines to raise the coal. In 1815 the first steam engine was used to draw the basket and pump out the water by the 'Anglesey Coal Company Ltd.' working the Berw coal. By 1840 the pits were 200 yards deep. Water was extracted by large powerful engines. The Berw stack and colliery buildings are the sole remains of the industrious Coal mines of Anglesey. By 1997 the stack, smithy, store-house, office and cottage of the Berw Colliery was in a ruinous state facing demolition on health and safety reasons. On the eleventh hour Donald Glyn Pritchard secretary of the Pentre Berw Conservation Society sent an SOS- 'Save Our Stack' plea to the Anglesey Antiquarian Society which resulted in
CADW within a fortnight sending two inspectors to Pentre Berw to inspect the site. D.G.Pritchard local representative of the AAS testified to the importance of listing the colliery. The site was listed by CADW and the buildings were reinforced and anchored by, RSPB (Cymru), Cadw and Rural Wales Council. The remains of the old Plas Berw was reinforced by the owners and CADW and the old church - Llanfihangel Pentre Berw was also restored and anchored by a grant from CADW. (Cadw report 2012) The colliery lies in RSPB Cors Ddyga which was opened to the public on 18 July 2017. ==Landmarks==