I sometimes wonder why every single variation in a cocktail requires an alternate naming scheme. In this case you have a fairly simple drink, gin and vermouth. One would think that these would be the determining factors, but no. In this case it is the garnish which determines the name. If you place a cocktail olive in the drink you have a martini, if instead you place an onion in the drink it becomes known as a Gibson.
Like many cocktails the Gibson’s creation is shrouded in mystery. It is entirely possible that the drink originated in many places at the same time as the components are not rare, difficult to combine or unusual. Regardless of the circumstances of its creation the drink is similar to the martini in all respects except for the item on the end of the toothpick.
Even further removed if you garnish the drink with an olive, an onion and another olive alternating on a toothpick the drink is called a Patton.
For those not familiar:
2.5 oz of gin
0.75 oz dry vermouth
Stir over ice, strain into coupe glass.
Garnish with cocktail onions.
You might ask how many, the best advice I’ve ever heard on the subject is as follows:
“Always add between one and three, but remember three is a meal and even numbers are unlucky. I’ll let you figure the rest out.”
Shaker and Spreadsheet 