The simple answer is the French. The precursor to tennis began in the 17th century, when French aristocrats ponced about in their gold-gilded palaces, swatting at balls. It sounds genteel, but the game was an evil den of irresponsible gambling, with people betting silver pieces on every point.

Each silver piece was worth 60 sous, a bronze coin used as currency at the time. Bets were laid on each points in quarters of silver - that is, 15, 30, 45 and 60 sous.

The scoring system survived, even when gambling was phased out.

However, 45, was reduced to 40 to keep the terms to two syllables or less - quarante instead of quarante-cinq. Then the scoring system became really bizzare.

Forty-all became deuce, from the French for two, deux, because at that stage of the game, either player needs two consecutive points to win the game.

The 'love' part comes from the French word for 'the egg', l'oef, since an egg looks like a zero.