Green’s Dictionary of Slang

shakedown n.

1. [early 19C+] an impromptu bed, somewhere to sleep, not necessarily a proper bed.

2. attrib. use of sense 1.

3. a boarding house.

4. in senses of extortion or coercion [the image of shaking one’s clothes (or cell) until money falls out].

(a) [mid-19C] (US Und.) a brothel where one is liable to be robbed.

(b) [mid–late 19C] (US) a rough dance.

(c) [late 19C+] blackmail, extortion; also attrib.

(d) attrib. use of sense 3c.

(e) [1910s+] a search, either of a person, a place or one’s belongings.

(f) [1910s+] (US prison) a search, whether of a cell or of an individual prisoner.

(g) [1930s+] a payment, a bribe.

(h) attrib. use of sense 3g.

5. see throwdown n.1

In compounds

shakedown artist (n.) (also shakedowner)

[1930s+] an extortionist, a blackmailer.