The Scoring System Comes from a Clock Face

the 15–30–40 tennis scoring system is widely believed to have originated from the use of a clock face, and here's how the theory goes:

• In early French tennis, scores were tracked using a clock dial.
• Players would advance the score by a quarter of the clock for each point won:
  • First point: 15 minutes
  • Second point: 30 minutes
  • Third point: 45 minutes
  • Fourth point (game): 60 minutes

• Over time, "45" was shortened to "40" — likely to make calls quicker and smoother (saying "forty" is faster than "forty-five").
• Another theory is that a jump from 30 to 40 maintains symmetry in scoring without reaching "full hour" (60), which represents the end of the game.

• At 40–40, the game isn't won yet — both players need to win two consecutive points:
  • Deuce: from the French à deux (both at two).
  • Advantage: the player who wins the next point after deuce.
  • Win the next point again = game.

While this "clock face" theory isn't officially confirmed, it's the most widely accepted historical explanation. It shows how tennis has retained some charmingly archaic traditions even in modern times.