“Piss or get off the pot”
The above phrase, meaning to cease procrastinating and do something (and, in some cases, to stop preventing others from taking action), is a derivation of the phrase “shit or get off the pot”. It is believed to date from the days when there was no indoor plumbing and when a chamber pot (also known as a “po” and a “gazunder”) was used for urination and defecation.
That phrase is believed to have developed from the older expression “fish or cut bait”, meaning do something productive or get out of the way and do something else so as to let others have a go. The phrase originated in the US in the mid 19th century.
A succinct comment to the same effect, by Thomas Paine (1737 – 1809):
"For six years that man has given me unsolicited advice—all of it bad. I was particularly offended by his comment to 'shit or get off the pot' in reference to my delay in calling for action in the Boston police strike."
- US President Calvin Coolidge,
commenting on his successor Herbert Hoover.