tor (n.)

"high, rocky hill," Old English torr "rock, crag;" said to be a different word than torr "tower." Obviously cognate with Gaelic torr "lofty hill, mound," Old Welsh twrr "heap, pile;" and perhaps ultimately with Latin turris "high structure" (see tower (n.)). But sources disagree on whether the Celts borrowed it from the Anglo-Saxons or the other way round.