Green’s Dictionary of Slang

knock out v.

1. (also bang out) in intransitive uses.

(a) [mid-19C+] to do roughly or quickly, esp. of writing, to create, to make etc.

(b) [late 19C+] (orig. Aus.) to earn a sum of money; e.g. knock out £200 per week; although orig. of food, in phr. knock out tucker.

(c) [late 19C+] to obtain for oneself, e.g. knock out some sleep.

(d) [20C+] to sell.

2. in transitive uses.

(a) [late 19C] to make someone bankrupt.

(b) [late 19C] to fail an examination candidate.

(c) [late 19C–1960s] (US) to deprive someone, esp. of money.

(d) [late 19C+] to kill someone; thus knock-out man n.

(e) [late 19C+] (orig. US) to surprise, overcome or defeat.

(f) [late 19C+] (esp. US black, also knock flat) to impress, to overwhelm, to delight.

(g) [1900s] (Aus.) in fig. use, to surpass.

(h) [1920s–40s] (US Und.) to arrest.

(i) [1940s–70s] to steal, esp. to steal everything from the place one is robbing.

In phrases

knock oneself out (v.) [1930s+] (orig. US)

1. to have a very enjoyable time, to ‘let oneself go’, to amaze oneself.

2. to work very hard.

3. to worry.

In exclamations

knock yourself out!

[1940s+] (US) have a good time!

SE in slang uses

In phrases

knock out of the box (v.) [baseball jargon]

[late 19C+] (US) to defeat, to overcome, to kill.

knock out one’s link (v.) [? SE link, ‘a torch...formerly much in use for lighting people along the streets’ (OED)]

[mid-18C] to be very drunk.