How was the margarita invented?

The exact origin of the margarita is shrouded in mystery, but historians have several theories. For one, the word margarita is Spanish for "daisy" and one historian believes the drink originated as daisy brandy and later used tequila instead. If you listen to Jose Cuervo, they suggest the drink was named for a Mexican showgirl Rita de la Rosa. There are several other origin stories listed in the article including a few of these...

The history of the margarita is shrouded in mystery and folklore due to its numerous origin stories. According to cocktail historian David Wondrich, the margarita is related to the brandy daisy (margarita is Spanish for "daisy"), remade with tequila instead of brandy. (Daisies are a family of cocktails that include a base spirit, liqueur, and citrus. A sidecar and gin daisy are other related drinks.) There is an account from 1936 of Iowa newspaper editor James Graham finding such a cocktail in Tijuana, years before any of the other margarita "creation myths".

The Cafe Royal Cocktail Book, published in the UK in 1937, contains a recipe for a Picador using the same concentrations of tequila, triple sec, and lime juice as a margarita. One of the earliest stories is of the margarita being invented in 1938 by Carlos "Danny" Herrera at his restaurant Rancho La Gloria, halfway between Tijuana and Rosarito, Baja California, created for customer and former Ziegfeld dancer Marjorie King, who was allergic to many spirits, but not to tequila. Herrera related this story and also by bartender Albert Hernandez, acknowledged for popularizing a margarita in San Diego after 1947, at the La Plaza restaurant in La Jolla. The story was debunked in 1992 by the San Diego Reader.

https://en.wikipedia.org/wiki/Margarita