Where does the food industry term "86" come from? [duplicate]

Solution 1:

"86" is most commonly used to refer to throwing something away or refusing service. From Wikipedia:

"86","86ed", "86'd", or eighty-sixed when used as a verb in American English, is a slang term for getting rid of something, ejecting someone, or refusing service.

Later in that article they do refer to the usage you mention:

1933, The most widely accepted theory of the term's origin states it derives from a code supposedly used in some restaurants in the 1930s, wherein 86 was a shortform among restaurant workers for 'We're all out of it.' Snippets of said code were published in newsman Walter Winchell's column in 1933, where it was presented as part of a "glossary of soda-fountain lingo."

They link to the Snopes article on the same term which provides slightly more detail:

The 86 of the restaurant code of the 1930s [...] never seemed to be reflected in anything other than newspaper articles touting the code itself. Given that slang common to its times seems to effortlessly work its ways into all sorts of popular culture outlets (novels, radio shows, plays, movies), that 86 apparently took until 1944 to appear in as much as even one book tends to argue against its being in common parlance at the time the restaurant code was supposedly all the rage. Also, when it did appear, it had nothing to do with "We're all out of that item," the supposed original meaning, but instead was a presentation of "Deny that fellow service," one popular form of its clear-cut current meaning.

So, to answer your question, there are enough references to your usage of "86" from the 1930s to suggest an origin during that timeframe but most of the speculation around the term doesn't care so much about the restaurant code.

Whether this particular usage of "86" is still in practice today is beyond my knowledge but I strongly suspect that nearly all modern references to "86" has nothing to do with the restaurant code and nearly everything to do with throwing something away or refusing service.