etech posted this earlier in another thread:
I believe 86 was a nautical term refering to deep water. To 86 something was to throw it overboard when the ship was in deep water where the item could not be recovered.
First I ever heard it was in the restaurant biz in 1985. When we were out of something, it was '86'. Being young at the time, I thought it had something to do with 1986. Wrong.