Old English clæne "free from dirt or filth; pure, chaste, innocent; open, in the open," of beasts, "ritually safe to eat," from West Germanic *klainoz "clear, pure" (cf. Old Saxon kleni "dainty, delicate," Old Frisian klene "small," Old High German kleini "delicate, fine, small," German klein "small;" English preserves the original Germanic sense), from PIE root *gel- "bright, gleaming" (cf. Greek glene "eyeball," Old Irish gel "bright").
"Largely replaced by clear, pure in the higher senses" [Weekley], but as a verb (mid-15c.) it has largely usurped what once belonged to