Smoo Cave

Smoo Cave is a large combined sea cave and freshwater cave in Durness in Sutherland, Highland, Scotland. The cave name, which was previously known as Smow(e) or Smo, may originate from the Norse 'smjúga' or 'smuga', meaning a narrow cleft, or hole. However, it could instead relate to the Gaelic word 'smùid', meaning fine spray (in relation to the cave's waterfall), or the Gaelic translation Uamh as Motha of "the Largest Cave" as it was also known according to Sir Walter Scott. The name Uamh Smùdha was introduced for purposes of bilingual signage at the site ca. 2010 and has since received use in Gaelic media.

Source: wikipedia