The Gibson is a classic, old school cocktail that is a variation on the Gin Martini where the olive or lemon twist is replaced with a cocktail onion. Interestingly, according to the oldest published recipe for the Gibson in the 1908 book, "The World's Drinks And How To Mix Them" by William Boothby, a Gibson is equal parts gin and French vermouth stirred with ice and strained into a cocktail glass and sometimes served with an olive. Except for the ratios, this sounds suspiciously close to a typical gin martini to me.
Quick Pickled Green Onions Recipe
1/2 C. Water