Why are zero scores in tennis called ‘love’?

BECAUSE: In France, where tennis became popular, the round  zero on the scoreboard looked like an egg and was called ‘l’oeuf’, which is French for ‘the egg’. When tennis was introduced in the US, Americans (naturally), mispronounced it ‘love’

Why do X’s at the end of a letter signify kisses?

BECAUSE: In the Middle Ages, when many people were unable to  read or write, documents were often signed using an X. Kissing the X represented an oath to fulfill obligations specified in the document. The X and the kiss eventually became synonymous.