mid-15c., "one of a series of rings or loops which form a chain," probably from O.N. *hlenkr (cf. O.Swed. lænker "chain, link," Norw. lenke, Dan. lænke), from P.Gmc. *khlankijaz (cf. Ger. lenken "to bend, turn, lead," gelenk "articulation, joint, link," O.E. hlencan (pl.) "armor"), from PIE base *qleng- "to bend." The verb (late 14c.) is believed to be from the noun, though it is attested earlier. Missing link between man and apes dates to 1880.