12-century French monks invented tennis.
This was the earliest precursor to tennis. The monks played the game indoors without any rackets.
They only used their hands! It was originally called “jeu de paume”.
The game eventually caught on among French nobility, and of course, they added rackets.
The name “tennis” comes from the French word “Tenez”, which was said before a serve.
The rest of tennis terminology comes from French as well; a lob is “un lob”, a fault is “une faute”, a break is “un break”, a volley is “une volleé”, etc.
Tennis eventually evolved to the outdoor sport we know today. The technical term for the outdoor sport is “Lawn Tennis”, as opposed to the game the monks invented, which we call “Real Tennis”.
More about tennis from LIVESTRONG and the New York Times.