Glen
A glen is a valley, typically one that is long, deep, and often glacially U-shaped, or one with a watercourse running through it. Whittow defines it as a "Scottish term for a deep valley in the Highlands" that is "narrower than a strath".
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. The word is sometimes found in tautological placenames where its meaning was opaque to a new linguistic community, an example perhaps being Glendale (literally "valley valley") which is a combination of Norse "dale" and Gaelic "glen".