Hi Brittany: This phrase originated in the 1930s according to the Chambers Slang Dictionary (which contains hundreds —one could say "shitload" — of colorful shit-related words and idioms over 6 pages, a testimony to people's fascination with biological functions, as Freudians will know). According to Google Ngram, this phrase, meaning "[stop wasting time and] make a decision" has been in steady use since the 1940s. Because idioms are informal, they are mainly used in speech rather than in print. I think just about everyone has heard (or used) this phrase. You can also try the more alliterative variation: "piss or get off the pot." No matter how you say it, it's a powerful and evocative idiom. Enjoy its use. Cheers. Alex