twistedness: words, plans, or people turned back to front, so that what ought to run straight comes out inverted
The picture behind this word is something turned over. It belongs to a family of Hebrew words about overturning, the kind of turning that flips a city onto its ruins, and it names what results when that same reversal happens to speech, to scheming, or to a person's whole outlook. It is not simply a bend in an otherwise straight line. It is straightness put the wrong way round.
Nine of its ten appearances are in Proverbs, and there it keeps close company with the mouth. Five times it is what a tongue produces, what a mouth is full of, or what a man is heard saying. Three times it moves inward, to the heart that turns crooked things over and the schemer who takes pleasure in them. Twice it stops describing an act at all and simply names what someone is: a man of it, a whole generation of it. The senses hold together because the inward twist and the twisted talk are one thing at two stages, the crooked heart and the crooked mouth it feeds.
Proverbs has several words for talk that has gone wrong, and they turn up in the same lists. Crookedness (עִקְּשׁוּת) pictures a line bent out of true, and deceit (מִרְמָה) names talk aimed at fooling a particular person. This word is more drastic than either. It is not a bend or a trick but a reversal: evil recommended as good, and the straight road pointed backwards.
That is what gives its one appearance outside Proverbs such weight. In the song at the end of Deuteronomy, God looks at Israel and calls them a generation of exactly this, children with no faithfulness left in them. Centuries later the New Testament brings the same charge with its own verb for twisting something out of shape (διαστρέφω), describing a crooked and twisted generation in the language of that song.