The name Kieth is a variant of the more common English name Keith, which has its origins in Scotland and northern England. It is derived from the Brittonic Celtic name Cái, which means "battle" or "warrior." The earliest known spelling of the name is "Ket," which dates back to the 12th century.

The name Keith is believed to have been introduced to Scotland by the Norman conquerors in the 11th century. It became particularly popular in the Scottish Highlands, where it was used by several prominent clans, including the Clan Keith and the Clan MacKie. One of the earliest recorded bearers of the name was Robert de Keith, a Scottish nobleman who lived in the 12th century and was the progenitor of the Clan Keith.

In the Middle Ages, the name Keith was often associated with military prowess and bravery on the battlefield. Several knights and warriors bearing this name are mentioned in medieval chronicles and records. For example, Sir William Keith, a 14th-century Scottish knight, was renowned for his valor and loyalty to King Robert the Bruce during the Wars of Scottish Independence.

Over the centuries, the name Kieth has been used by various notable individuals, including Kieth Jarrett (born 1945), an American jazz pianist and composer; Kieth Mitchell (born 1946), an American professional basketball player; and Kieth Lee (born 1983), an English professional wrestler.

Other historical figures bearing the name Kieth or its variants include Kieth Merrill (1925-2021), an American actor and director; Kieth Rendleman (1894-1974), an American politician and lawyer; and Kieth Stroup (1781-1838), an American pioneer and frontiersman.

It is worth noting that while the name Kieth is a variant spelling of Keith, it has been used independently by some individuals and families throughout history. Regardless of the spelling, the name has maintained its connection to its Celtic roots, evoking a sense of strength, courage, and warrior spirit.