Australian Open
Why is the scoring so strange in tennis, with 15, 30 and 40 points per ball?
Strange for you, who was born in the 21st century and got used to measuring life in the predictable decimal metric system. At the time of Jeu de Paume, a French sport that is one of the origins of modern tennis and that began to be played in the 16th century, this sexagesimal score made perfect sense. Think about your clock: the first dot represents a quarter of the circle, or 15 minutes; the second half circle, and so on until the game (formerly 60 points). But if this is so, why 40 and not the logical 45? Because in French, the language of the people who created the Jeu de Paume, it is much easier to shout "quarente" in the heat of the game than the long “quarent-cinq”. Thus, time took care of making the famous short a standard. In the 1970s, Americans tried to change the scoring to a boring 1, 2, 3 and game, but the idea didn't work.
Source: Playboy Magazine