Survey of English Place-Names

Etymology

Cob Castles, 1841 O.S., referring to loose rocks and stones at the highest point above Wharncliffe Rocks. The name, which occurs elsewhere, may contain OE  cobbe 'a round lump', possibly 'a hill, the peak of a hill', and castel, but in YW usage a cob-castle is 'a building overtopping those near it' and also 'a flimsy building' (v. EDD s.v. cobb sb.1). These definitions may originate as descriptive interpretations of the names of such places which are in lofty situa- tions or merely ruinous remains of old structures. The word thus came to be used of a heap of loose rocks.