"clear, open space in a woods," c.1400, 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).