"86" and Route 86 (folk etymology)

[bapopik at AOL.COM]

I ate Sunday at Mustang Sally's (est. 1993). It's on Seventh Avenue in the 30s, near Madison Square Garden. It has the same owner as Mustarng Harry's a block or two away. The name comes from a song in THE COMMITMENTS.
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It's good pub food. There were many big tv screens to watch my NJ Nets get killed.
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I asked several people if there was any slang, maybe in food service or associated with the Garden. Of course, I got nothing. I mentioned "86." They'd heard of that.
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The bartender volunteered that it came from "Route 86," which couldn't be completed in the Rocky Mountains, so "86" was anything that wasn't available.
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Of course, I'd found "86" in the early 1930s, and there wasn't even a Route 86, AFAIK. But add another one to the books.