"Help! Help!" began Jim Murray's letter, waking me out of my usual Monday morning stupor. "Can you or any of your intelligent readers explain the origin of the term '86,' meaning 'You're cut off'? Season ticket holders at the Golden Bull in Adelphi have all been trying to find out . . . . "

It was strictly palms up in this corner, Jim. I had no idea. I hunted down a guy in the newsroom who's a well-known trivia trove. A stumper for him, too.

Then I called a few friends who have been known to frequent bulls far less golden than yours, Jim. They not only didn't know, but they said they'd never heard the expression before.

To the rescue: The American Thesaurus of Slang, which dates '86' to soda fountains of the 1920s, of all places.

Eighty-six was a code uttered by one soda clerk to another. It meant, "We're all out of the item your customer ordered." The expression migrated from soda fountain to bar during the next decade. In bars, it's used when one bartender wants to tell another, "Don't serve that guy any more because of the shape he's in."

Were there other numerical codes in the soda fountains of yesteryear? Absolutely, says the thesaurus.

The head fountain manager was a 99. His assistant was a 98. But 98 from one clerk to another also meant, "The assistant manager is prowling around. Watch out."

Nineteen meant a banana split. Thirty-three stood for a cherry Coke. Fifty-five indicated root beer. And 87 1/2 meant, "There's a good-looking girl out front."

Hope that unmuddies the waters, Golden Bullers. May there be many occasions for all of you to say 87 1/2 as you sip your 33s. As for this item, 86.