1) A heap of slag or scorić, the dross thrown off from iron in a bloomery or forge.
1584 a parcel of waste at Fenay Bridg End, being a Synder Hill, Lepton. It occurs as a by-name and minor place-name, with early examples in the Sheffield area: 1297 Ricardus de Scynderhill, Handsworth
1379 Johannes de Syndirhill, Sheffield. This place-name cannot now be identified but it is on record in 1200-18 and serves as further evidence for the early smelting of iron ore. Elsewhere in Yorkshire the place-name is frequent, and it helps archaeologists and historians to identify old forge sites. Canon Atkinson listed 48 locations in Cleveland where ‘cinder hills’ existed in 1884, including those at Cinder Dyke, Furnace Farm, Pitholes and Smithy Holm. It actually derives from the Old English word sinder which meant ‘slag’ and the present spelling shows the influence of ‘cinder’ which has a French origin and means ‘ashes’. The dross was used by road-makers and many former cinder hills have disappeared.