There is no evidence of its origin, but these are the three most popular theories:
1. derives from the French expression for "the egg" (l'oeuf) because an egg looks like the number zero. This is similar to the origin of the term "duck" in cricket, supposedly from "duck's egg".
2. comes from the Dutch expression iets voor lof doen, which means to do something for praise, implying no monetary stakes.
3. comes from the acceptance that, at the start of any match, when scores are at zero, players still have "love for each other".