Green’s Dictionary of Slang

tack n.1

[SE tack, solidity or tackle, food]

1. [mid-19C] (UK Und.) in pl., money, either notes or coins.

2. [mid-19C+] (orig. naut.) food, ship’s biscuit.

3. [mid-19C+] drink.

4. [1950s] money [separate development to sense 1].

In phrases

break the tack (v.)

[1910s] to drink after a period of abstinence.

go on the tack (v.)

[1910s] to abstain from alcohol [? SE tackle].

soft tack (n.)

1. [mid–late 19C] (orig. naut.) bread as opposed to biscuits or hard tack.

2. [late 19C-1910s] (Aus.) a soft drink, as opposed to hard liquor.