kink (n.)
1670s, "knot-like contraction or short twist in a rope, thread, hair, etc., originally a nautical term, from Dutch kink "twist in a rope" (also found in French and Swedish), which is probably related to Old Norse kikna "to bend backwards, sink at the knees" as if under a burden (see kick (v.)). Figurative sense of "odd notion, mental twist, whim" first recorded in American English, 1803, in writings of Thomas Jefferson; specifically "a sexual perversion, fetish, paraphilia" is by 1973 (by 1965 as "sexually abnormal person").
kink (v.)
1690s (intransitive), 1800 (transitive), from kink (n.). Related: Kinked; kinking.