The name Brett has its origins in the medieval Breton language, a Celtic Brittonic language spoken in the historical region of Brittany in modern-day France. The name is derived from the Breton word "briz," meaning "broken" or "splintered," and may have been used to describe someone with a boisterous or unruly nature.

The earliest recorded use of the name Brett can be traced back to the 12th century, where it appears in various Breton and Norman records. It is believed that the name was brought to England by Norman settlers after the Norman Conquest in 1066, and gradually gained popularity among the English nobility and gentry.

One of the earliest notable figures to bear the name Brett was Sir Brett Whitshed (c. 1272 - 1349), an English knight and landowner who fought in the Hundred Years' War against the French. Another historical figure was Brett Harte (1836 - 1902), an American author and poet best known for his short stories depicting life in the American Old West.

In the 16th century, the name became associated with the Brett family, a prominent English noble family with roots in Somerset and Dorset. One notable member was Sir Peter Brett (1510 - 1568), a member of the English Parliament and a supporter of the Protestant Reformation under King Edward VI.

During the 17th and 18th centuries, the name continued to be popular among the English upper classes, with several notable figures bearing the name. These included Brett Whitehead (1652 - 1728), an English lawyer and Member of Parliament, and Brett Westcott (1695 - 1774), a British naval officer who served in the Royal Navy during the War of the Austrian Succession.

Moving into the modern era, one of the most famous individuals with the name Brett was Brett Favre (born 1969), an American professional football player who played quarterback in the National Football League (NFL) for 20 seasons. Other notable Bretts include Brett Butler (born 1958), an American actress and comedian, and Brett Whiteley (1939 - 1992), an Australian avant-garde artist known for his innovative techniques and bold use of color.