I have never looked up the etymology of the phrase “out of pocket” meaning “totally unreasonable and ridiculous” but in my pharmacy tech heart and soul I know that it means “like the amount your medication would cost without insurance”
I am not disagreeing with your pharmacy tech heart and soul or indeed what people may generally associate the phrase with here in the present day!
But I was curious about the etymology, and this blog post says:
According to the newest edition of Cassell’s Dictionary of Slang, “out of pocket” is a variation on the phrase “out of (the) pocket,” a 1940s African-American expression referring to bad behavior or a bad situation. Cassell’s says this meaning grew out of pool jargon (a shot that was “out of pocket” or “out of the pocket” caused a player to miss a turn).
And Merriam-Webster agrees that this sense comes from African American English and was first recorded in the mid-20th century.
So that was fun to learn, thanks for the prompt to look it up!