Caught in passing on a tv show, a character talking about cop-talk:
Hinky? That’s not even a word!
Like every other cry of “That’s not a word!”, this one is bullshit.
Start with the very short story, from NOAD2:
US informal (of a person) dishonest or suspect: he knew the guy was hinky. (of an object) unreliable: my brakes are a little hinky. ORIGIN 1950s: of obscure origin