Green’s Dictionary of Slang

shake down v.

1. in senses of shakedown n. (1)

(a) [mid-19C+] to sleep in an impromptu bed.

(b) [late 19C] to settle into living quarters.

2. (also shake loose, shake out) in senses of shakedown n. (4)

(a) [mid-19C+] to blackmail, to extort money (from); thus shaker-down n., a blackmailer.

(b) [late 19C+] to interrogate; to elicit information.

(c) [late 19C–1910s] to obtain a financial contribution from, e.g. to a political campaign.

(d) [20C+] (also shake, of (usu.) police, to search, to raid; also (prison) to search a cell.

(e) [1910s] to check one’s pockets (for cash).

(f) [1910s] to pay protection to the police against one’s will.

(g) [1930s+] to rob.

(h) [1950s] to empty out.

(i) [1990s+] (US black) to have sex with.

3. [1990s+] to beat at cards.

In phrases

shake it down (v.)

[2000s] to make an effort, to get to work.