Do you know ghouls from goblins and ghosts?
"narrow valley," late 15c., from Scottish, from Gaelic gleann "mountain valley" (cf. Old Irish glenn, Welsh glyn). Common in place names; cf. Glenlivet (1822), a kind of whiskey, named for the place it was first made (literally "the glen of the Livet," a tributary of the Avon); and Glengarry (1841) a kind of men's cap, of Highland origin, named for a valley in Inverness-shire.