Etymology: Occurs as an element in topographical names in early West Saxon charters; also, as a local term for a topographical feature from Old English onward. Generally held to be Celtic; but, though frequent in place-names in Cornwall, Devon, etc., not recorded as a ‘common noun’ in Cornish or Breton. In Welsh the nearest word is apparently tŵr (= /tur/), Old Welsh twrr ‘heap, pile’ (rare in place-names, but compare Mynydd Twrr , old name of Holyhead Mountain, Rhŷs). Probably cognate with Gaelic tòrr ‘hill of an abrupt or conical form, lofty hill, eminence, mound, grave, heap of ruins’ (Macleod and Dewar), primarily ‘heap, pile’, compare tòrr verb ‘to heap up, pile up, bury’, Irish torraim ‘I heap up’, and the derivative Gaelic torran ‘little hill, knoll, hillock’, Irish torrán ‘heap, pile, hillock’. Compare also quot. 1905 at sense 1a.

Etymology: The Old Norse and Old English adverbial particle tor- ‘hardly, with difficulty, ill-’, used especially with verbal adjectives as in Old Norse tor-fengr hard to get, tor-næmr hard to learn, tor-sýnn hard to see, tor-talinn participle, counted with difficulty, tor-tryggr hard of belief; also Old English tor-cyrre hard to turn or convert, tor-begéte hard to get. In Middle English, especially in those parts in which the Norse influence was strong, this particle was treated as a separate word, in the sense ‘hard, difficult, ill’, and was used especially with the infinitive, as tor (for) to tell, tor for to ken; the former of these was a favourite phrase of the alliterative poets. In some instances, as already in Ormin, tor alone was used attributively. Old Norse and Old English tor- were cognate with Old High German zur-, Gothic tuz-, Greek δυς-, Sanskrit dus-, hard, evil, ill-: with the Old Norse and Old English words compare Greek δυσαής ill-blowing, δύσβρωτος hard to eat, δυσμαθής difficult to learn. Senses 2, 3 appear to be the same word, but the change of sense is remarkable.