The Side Car is a classic cocktail made with equal parts Cognac, Cointreau and lemon juice. The recipe was first published in 1922 in "Cocktails: How to mix them" by Robert Vermeire, where the author indicates that the Side-Car was "introduced" to Buck's Club in London by bartender Pat MacGarry.
But since "introducing" does not necessarily mean "having created", the true origin of the Side-Car is debated. Indeed, by publishing this recipe in 1922 Robert Vermeire also indicates that this cocktail is very popular in France, which could attribute this recipe to Franck Meier of the Ritz in Paris, or to Harry Mac Elhone of New York's Bar / Harry's Bar in Paris, but this last hypothesis seems ruled out since Harry Mac Elhone himself would have attributed this cocktail to the Buck's Club in London in 1922. In short, we're going around in circles...
Concerning the origin of the name of this cocktail, several hypotheses also exist but it seems that the name pays homage to an army officer who used to go to the bar in a sidecar.
Just like its origin, the dosages of the cocktail are also much debated, in truth it is only a question of personal taste but as you can see below the original recipe published in 1922 indicates anyway ingredients in equal parts.