1. in context of alcohol.
(a) [17C+] (also soak up) to drink heavily.
(b) [19C] to ply with liquor.
(c) [1900s] to spend money on drink.
2. in monetary senses.
(a) [mid-19C–1920s] to pawn; to give as collateral.
(b) [1900s–40s] (US campus) to borrow [one leaves one’s possession ‘to soak’].
(c) [1900s] (US) to put away.
3. see let it soak
[mid-19C] very drunk.
1. [mid–late 19C] in prison.
2. [mid-19C+] in pawn; thus soak n., pawn, a pawnshop; thus antonym out of soak.
3. [late 19C] (Aus.) drunk.
SE in slang uses
[late 19C+] of a man, to linger before withdrawing one’s penis after intercourse.
see moisten the clay under clay n.
[late 18C+] to drink, to quench one’s thirst.
see under chaffer n.2
[late 19C] (US) to drink away one’s possessions.
[mid–19C+] an abusive, dismissive remark.