O.E.
glæd "bright, shining, joyous," from P.Gmc.
*glathaz (cf. O.N.
glaðr "smooth, bright, glad," O.Fris.
gled, Du.
glad "slippery," Ger.
glatt "smooth"), from PIE
*ghledho- "bright, smooth" (cf. L.
glaber "smooth, bald," O.C.S.
gladuku, Lith.
glodus "smooth"), from PIE base
*ghlei- "to shine, glitter, glow, be warm" (see
gleam). The modern sense is much weaker.
Gladden is O.E.
gladian "be glad, make glad" +
-en. Slang
glad rags "one's best clothes" first recorded 1902.
Glad hand "the hand of welcome" (often used cynically) is from 1895.