The word is also found in other Brythonic languages, including Welsh ("twr" - tower) and Breton ("tour" - tower).
While "tor" can be used to describe a rocky hillside, its primary meaning is a peak or a high point.
Here are some Celtic words for hillside:
* Welsh: "bryn" (hill, slope)
* Irish: "cnoc" (hill), "sliabh" (mountain)
* Scottish Gaelic: "cnoc" (hill), "beinn" (mountain)
* Manx: "cregg" (rock), "kione" (peak)
So, while "tor" is a Celtic word, it doesn't refer to a hillside in general but rather a specific type of rocky elevation.