Etymology of "informal British" word "bent" (meaning: dishonest, corrupt)

Question

I have been seeing some of my British friends using the word "bent" to mean dishonest, cheater, immoral etc. "Bent" as adjective is defined in Lexico as British informal Dishonest; corrupt.

I wonder where it got this sense. I searched different etymology dictionaries such as Wikitionary, Online Etymology Dictionary (Etymonline), Etymology Online, Etymology Geek but none of them says anything about this sense of "bent".

Etymonline has a note about the adjective "bent" but it is about the shape (curved). I have no access to Green Dictionary of slang. Can someone tell me where "bent" acquired this sense?

Answer 1

It apparently derives from the expression:

on the bend (adj.)

1. crooked, criminal, underhand [predates bent adj. (3) but presumably its derivation].

• 1863 [UK] J.C. Jeaffreson Live it Down II 152: I never have paid anything yet on the square, and I never will. When I die, I’ll order my executor to buy my coffin off the square. He shall get it on the bend somehow or other [F&H].

Bent :

3. criminal; corrupt; thus on the bend under bend n.1 ; thus bent copper, bent screw, corrupt police officer, prison-warder.

• 1914 [US] Jackson & Hellyer Vocab. Criminal Sl. 17: bent [...] crooked; larcenous. Example: His kisser shows that he’s bent. Blockquote
• 1931 [US] Irwin Amer. Tramp and Und. Sl. 26: Bent.—Crooked ; criminal ; outside the law. Directly the opposite of ‘straight,’ and applied to individuals, enterprises or goods.

(GDoS)

But probably as a synonym of crooked whose figurative sense of dishonest dates back to the 13th century.

early 13c., "bent, curved, in a bent shape,". In the figurative sense of "dishonest, false, treacherous, not straight in conduct" is from c. 1200.