Gythred, n. channel of a stream
Gythreden, n. a rivulet
Gwythwr, n. an angry man
Gwyw, withered, faded; feeble
Gwywder, n. faded state
Gwywel, n. withered vegetation
Gwywiad, n. a withering
Gwywo, v. to wither, to fade
Gwywol, a tending to wither
Gybain, v. to wail, to moan