In tennis, as in all things, love is shrouded in mystery. Some claim that it was derived from the French for egg, “l’oeuf,” since an egg resembles zero. Lexographers at Oxford University Press disagree. They think it’s more likely a version of ‘for the love of the game,’ that is, for nothing.
The whole tennis scoring system is a bit of an enigma. It seems that the modern rules were formalized by the Marylebone Cricket Club in 1876. They adopted the deuce-advantage scoring system in favor of a first-to-15 game that was also common.
The scores 15-30-40 are said to have Medieval French origins. Some say that they represent the cardinal points on a clock, used in scoring. The 40 should be 45, but is apparently just rounded down to 40. Others say that 60 was simply a lucky number in medieval France (The base 60 clock incidentally goes back to Babylonians). Most historians think that “deuce” is a version of “deux” or two. It means you need two successive points to win. “Ad” or “Advantage” means what it says, or so we think.