Are yams and sweet potatoes the same?
Old English hlanc "loose and empty, slender, flaccid," from Proto-Germanic *khlankaz, perhaps from a root meaning "flexible" (cf. German lenken "to bend, turn aside," Old Norse hlykkr "bend, noose, loop"), from PIE root *kleng- "to bend, turn" (see link (n.)). "Some examples may be long adj. with unvoicing of g" ["Middle English Dictionary"]