One theory suggests it comes from New York’s 86 Bedford Street, where police would call speakeasies and tell them to “86” (get rid of) the customers, who would then exit through the backdoor on that street. 86 is also one of many codes once used by soda fountain employees to communicate quickly among themselves. Code 33 meant a cherry-flavored Coke, Code 19 meant a banana split, and Code 86 meant they were out of a particular item. As a result, if a cook “86’d” an order, it meant he was cancelling it.
This slang term, which dates back to the 1930s, serves as quick, effective communication between kitchen staff and servers to inform them they should stop taking orders for that particular dish or product.
The Haus of Dcaligari 