Name for valley commonly used in Ireland, Scotland and the Isle of Man
A glen is a valley, typically one that is long and bounded by gently sloped concave sides, unlike a ravine, which is deep and bounded by steep slopes. The word is Goidelic in origin: gleann in Irish and Scottish Gaelic, glion in Manx. The designation "glen" also occurs often in place names. Glens are appreciated by tourists for their tranquility and scenery. Etymology. The word is Goidelic in origin: gleann in Irish and Scottish Gaelic, glion in Manx. In Manx, glan is also to be found meaning glen. It is cognate with Welsh glyn.
https://en.wikipedia.org/wiki/Glen