Everyone agrees the Negroni is named after a Negroni. The argument is over which one.
The familiar version is set in Florence. Count Camillo Negroni, a regular at Caffè Casoni, asked the bartender Fosco Scarselli for a stronger Americano. The Americano was Campari and Italian vermouth lengthened with soda. Scarselli swapped the soda for gin and, in some tellings, the lemon peel for orange.
Merriam-Webster gives this as the probable source of the name. It describes Camillo, or Cammillo, as an Italian nobleman who died in 1934 "for whom the drink was allegedly first mixed." It credits the Florence account to the Italian barman Luca Picchi, who places the drink between 1917 and 1920. The usual date in retellings is 1919.
The trouble is the paperwork. The Wine and Spirit Education Trust says the Florence story has "little documented evidence beyond hearsay" and that no early Italian written record has turned up. It does cite a British recipe from 1955, served on ice with an orange garnish.
A rival claim comes from the Negroni family itself. Noel Negroni has argued that the inventor was Pascal Olivier, Count de Negroni, a Corsican war hero who led a cavalry charge in the Franco-Prussian War of 1870. In this account he created the drink while stationed in Senegal and dedicated it to his future wife. Letters mentioning the drink support the claim, according to the Alcohol Professor site. The WSET dates the story to 1857 and quotes the letter calling it a "cocktail I invented ... based on vermouth."
That drink cannot have been today's Negroni. Campari was only founded in 1860, so the Corsican count's mix had vermouth and no Campari.
Noel Negroni also argued that no Count Camillo appears in the family histories. Later research by Rusty Hawthorne found that a Camillo Negroni did exist and was apparently some kind of count. Most of the colorful biography attached to him, though, remains unproven.
The word itself is simple. Merriam-Webster records "Negroni" in English from 1947, and it is often written with a capital letter, a reminder that a person stands behind the drink. Which person is still open.