The origins of tennis game, as any other game of racket and ball, are traditionally credited to 11th or 12th century French game paume which was played with the hand and later advanced into jeu be paume with the use of rackets. However, not all historians agree on this subject. There is a theory that the word tennis comes from the name of Tinnis, a town in ancient Egypt, and the word racket from rahat, meaning palm of the hand in Arabic. It is believed that different versions of the game were played in ancient Egypt, Rome and Greece, although there is no additional evidence to that. The balls initially used in tennis were made of hair, wool or cork wrapped in cloth or leather. The true history of tennis begins in the 1850s, when Charles Goodyear, of Goodyear tire fame invented vulcanized rubber, and the first rubber tennis balls were introduced to the world. The vulcanization of rubber is a process that prevents natural rubber from deteriorating so quickly. Nowadays, tennis balls are manufactured using high technology equipment, come in white or yellow colors, and all the specifications are regulated by the ITF (International Tennis Federation). Walter Clopton Wingfield is usually given credit for the invention of modern tennis. He actually patented the game in 1874, pronounced a new set of rules and moved tennis from indoors to outdoors. The same year first tennis courts appeared in the United States, and shortly after that in Russia, India, Canada and China. The first tennis championship was held in 1877 in Wimbledon, and is still considered the most prestigious one. US Open came into being a while later in 1881. Now there are four Grand Slam tennis tournaments: US Open, French Open, Australian Open and Wimbledon. The US Open tennis tournament was borne from two distinct tournaments -- US National Singles Championship for men and US Womens National Singles Championship, which were combined and renamed into US Open in 1968. Since then tennis has become a huge commercial and entertaining event with tennis tournament tickets for the public and various sponsors and advertisers. Sony Ericsson Open was founded in 1985 by a tennis player Butch Buchholz with the aim to make it number one tennis tournament of the year, or at least second after Wimbledon. His attempt failed, although this championship is considered to be the 5th most important tennis event of the year. It is traditionally held in Florida in March-April, the prize money is $9 million, and Sony Ericsson tennis tickets can cost up to $2000.