clank (v.)
1610s, perhaps echoic, perhaps a blend of clang (v.) and clink (v.), perhaps from a Low German source (compare Middle Dutch clank, Dutch klank, Old High German klanc, Middle Low German klank, German Klang).
clank (n.)
1650s, from clank (v.). Reduplicated form clankety-clank attested from 1895.