Onliest one I know - and it is possibly apocryphal.
There once was an American Ambassador who often had host cocktail parties where the preferred drink was a Maritini. Since the Ambassador did not want to get drunk he instructed the bartender to fill his Martini glass with water, and to distinguish his water from the gin-vermouth variety, he further instructed the bartender to put two pickled onions in the drink instead of the usual olive so he would always know which drink was his when presented with a tray of Martinis.
The Ambassador was eventually foiled when people started asking for their martini with onion instead of olive. The drink soon became known by the Ambassador's name : Gibson.
So - there you go - a real Gibson is water and two pickled onions in a cocktail glass, not a Martini with onion instead of olive!
As an aside : a sign hangs above the door of a rustic cabin on a New Hampshire lake which is owned by friends and which was built by the men of that family.
The sign reads : "Without the help of Tom Collins this cabin never would have been built."
