According to popular belief, one can tell the age of a rattlesnake by the number of rattles present at the end of its tail. A baby rattlesnake is born with the first segment of its rattle, called a "button". As the snake grows (and with each molting of its outer skin) an additional segment is added to its rattle. Younger snakes shed more often than older snakes, but on average, free-ranging snakes may molt three to six times a year. Another clue to a snake's age is its color: timber rattlers darken as they age, and the darkest are old males. The scientific name, Crotalus horridus, is formed from two Latin words: crotalum, meaning "bell or rattle," and horridus, for "dreadful"—which makes reference to its venom."
Source(s):
http://www.tpwd.state.tx.us/huntwild/wild/species/timberrattlesnake/
