piss-pot (n.)

"to urinate, discharge the fluid secreted by the kidneys and stored in the urinary bladder," c. 1300, pissen, from Old French pissier "urinate" (12c.), from Vulgar Latin *pissiare, of imitative origin. To piss away (money, etc.) is from 1948. Related: Pissed; pissing. Pissing while (1550s) once meant "a short time."

He shall not piss my money against the wall; he shall not have my money to spend in liquor. [Grose, "Classical Dictionary of the Vulgar Tongue," 3rd edition, 1796]

To piss money on the walls "throw money around recklessly" is attested from 1540s.

He who once a good name gets,

May piss a bed, and say he sweats.

["Dictionary of Buckish Slang, University Wit and Pickpocket Eloquence," London, 1811] 

"deep, circular vessel," from late Old English pott and Old French pot "pot, container, mortar" (also in erotic senses), both from a general Low Germanic (Old Frisian pott, Middle Dutch pot) and Romanic word from Vulgar Latin *pottus, which is of uncertain origin, said by Barnhart and OED to be unconnected to Late Latin potus "drinking cup." Similar Celtic words are said to be borrowed from English and French.

Specifically as a drinking vessel from Middle English. Slang meaning "large sum of money staked on a bet" is attested from 1823; that of "aggregate stakes in a card game" is from 1847, American English.

Pot roast "meat (generally beef) cooked in a pot with little water and allowed to become brown, as if roasted," is from 1881. Pot-plant is by 1816 as "plant grown in a pot." The phrase go to pot "be ruined or wasted" (16c.) suggests cooking, perhaps meat cut up for the pot. In phrases, the pot calls the kettle black-arse (said of one who blames another for what he himself is also guilty of) is from c. 1700; shit or get off the pot is traced by Partridge to Canadian armed forces in World War II. To keep the pot boiling "provide the necessities of life" is from 1650s.