PIE *ghel「輝く、光る」から。 語源的にはガラス、黄金と同じ。 密林の中の明るい場所、森の空き地を指すのに使われる。
英語の語源
glade (n.)
"clear, open space in a woods," late 14c., of uncertain origin, perhaps from Middle English glode (c. 1300), from Old Norse glaer "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).