Green’s Dictionary of Slang

whack n.1

also wack
[ext. uses of whack v.1 (1)]

1. [late 18C+] a share, a portion.

2. [early 19C+] a swig of a drink, a gulp of food.

3. [late 19C] (US) a bargain.

4. [late 19C+] (US) a try, an attempt.

5. [late 19C+] a ‘go’, a time.

6. [1950s] (US) an aspect.

7. [1980s+] (W.I.) a large sum of money.

8. [1990s+] (drugs) a portion of a drug, e.g. a ‘line’ of a narcotic, a puff of cannabis.

9. [1990s+] (Aus.) a bet.

10. [2000s] income.

11. see whacker n.1

In phrases

cop one’s whack (v.)

to get or take a share.

get a whack at (v.)

[1900s] (US) to gain access to.

go whacks (v.)

[mid-19C–1940s] to take or offer a share.

have a whack at (v.) (also take a whack at, ...whang at)

[late 18C+] (orig. US) to make an attempt or attack upon.

have one’s whack (v.) (also take one’s whack)

[mid-19C+] to have or take one’s share.

into whack [SE whack, to hit a blow, i.e. ref. to that which has been knocked home properly]

[1930s] into order.

put (someone) in the whack (v.)

[1980s] to give (someone) a share.