"clear, open space in a woods," late 14c., of uncertain origin, perhaps from Middle English glode (c. 1300), from Old Norse glaðr "bright" (see glad). If so, the original meaning could be "bright (because open) space in a wood" (compare French clairière "glade," from clair "clear, bright;" German Lichtung "clearing, glade," from Licht "light"). American English sense of "tract of low, marshy grassland" (as in Everglades) recorded by 1789, perhaps 1724 in place names (in Maryland).
