rough land, land with surface reminiscent of bark

In The Origin and History of Irish Names of Places (1910: I, 464), Joyce suggested that the element rúscaigh was related to the noun riasc “Marsh; bogland, moor” (FGB).. It seems more likely, however, that it is a substantive form of the adjective rúscach “possessing bark, barky” (DIL); “Bark-like; (of skin) rough, wrinkled” (FGB). It may be the case that rúscaigh is used in an imaginative sense in placenames with a meaning along the lines of “rough land”, an allusion to the rough texture of bark. In this context, it is worth noting that John O’Donovan interpreted the placename Rúscaigh/Roosky in the barony of Kilmacrenan as meaning “rough pasture”.
There are seven townlands by the name of Rúscaigh in County Donegal. (CÓC, JÓG)