The name Billy is a diminutive form of the name William, which has its origins in the Germanic languages. The name William is derived from the Old German name "Willahelm," which means "will" and "helmet." This name gained popularity during the Middle Ages and was brought to England by the Normans after the conquest in 1066.

The name Billy first appeared as a nickname for William during the 16th century. It was commonly used as a familiar or affectionate form of the name, particularly among the lower classes and in rural areas. Over time, Billy became a standalone given name in its own right.

One of the earliest recorded examples of the name Billy can be found in the works of William Shakespeare, who used the name in his play "The Merry Wives of Windsor" in 1602. In this play, one of the characters is referred to as "Billy Boy."

Throughout history, several notable figures have borne the name Billy. One of the most famous was Billy the Kid (1859-1881), whose real name was Henry McCarty. He was an outlaw and gunfighter of the American Old West, known for his involvement in the Lincoln County War in New Mexico.

Another well-known Billy was Billy Graham (1918-2018), an American evangelist and Christian minister who was influential in the evangelical Protestant movement during the 20th century. He held large outdoor rallies and encouraged personal conversion, becoming one of the most prominent religious leaders of his time.

In the world of sports, Billy Mills (born 1938) is a renowned American former track and field athlete. He is best known for winning the gold medal in the 10,000-meter run at the 1964 Tokyo Olympics, which was considered one of the greatest upsets in Olympic history.

Billy Wilder (1906-2002) was a famous Austrian-American filmmaker, screenwriter, and producer. He is widely regarded as one of the most brilliant and versatile filmmakers of Hollywood's Golden Age, directing classic films such as "The Apartment," "Some Like It Hot," and "Sunset Boulevard."

Finally, Billy Idol (born 1955) is a British singer-songwriter and musician who gained popularity during the punk rock and new wave movements of the 1970s and 1980s. Some of his most famous hits include "Rebel Yell," "White Wedding," and "Mony Mony."