"If anyone asks you where the term 86 originated, tell them what I tell people: I don't really know, but there are ... [View all]
...about 86 theories."
What Are the Origins and Meaning of 86?
This slang term dates back to the 1930s.
https://www.history.com/articles/86-meaning
One note in the article stands out:
By the 1950s, according to Merriam-Webster, 86 became a verb, commonly referring to tossing drunken customers out of bars...
Although Merriam-Webster notes some equate 86 with to kill, it adds this use is infrequent: We do not enter this sense, due to its relative recency and sparseness of use.
I read "relative recency" as "since Comey posted his picture" and "sparseness of use" as "nobody actually uses it this way, but Trump and his cadre claim that's what it means."
Most origin stories are related to restaurant and bar usage. Either being out of something (86 as code for don't take orders, we're out) or a person being 86's (don't serve them, kick them out).
Unconfirmed theories for the term "86" abound. Here are a few of the more popular origin stories, according to St. Louis Magazine columnist George Mahe:
Bartenders warned patrons of Prohibition raids at New York speakeasy Chumleys, located at 86 Bedford St., with 86: a warning to get the customers out via the bars 86 Bedford St. door to avoid the police arriving at a different entrance.
Article 86 of the U.S. Uniform Code of Military Justice concerns Absence Without Leave, or AWOL.
Great Depression soup kitchen pots served 85 people. So the 86th person was out of luck.