The name Kelis is believed to have originated from the ancient Greek word "kelis," which means "slender" or "graceful." It first appeared in written records during the Hellenistic period, around the 3rd century BC, in various parts of ancient Greece.

One of the earliest known bearers of the name was Kelis of Ephesus, a renowned philosopher and mathematician who lived in the 2nd century BC. Her works on geometry and number theory were highly influential in the ancient world.

In the 1st century AD, the name Kelis is mentioned in the writings of the Roman historian Pliny the Elder, who referred to a skilled potter from the city of Corinth bearing this name.

During the Byzantine Empire, the name Kelis gained popularity among Greek Christians, as evidenced by several notable figures from this era. Saint Kelis of Constantinople (542-619) was a revered abbess and founder of the Monastery of the Theotokos.

In the Middle Ages, the name Kelis appeared in various European regions, particularly in Italy and France. Kelis de Montfort (1180-1241) was a notable French noblewoman and crusader who participated in the Albigensian Crusade.

Another historical figure bearing the name was Kelis di Firenze (1310-1388), an Italian painter and illuminator from Florence, renowned for her artistic contributions to the Renaissance era.

In more recent times, the name Kelis has been associated with the American singer-songwriter Kelis Rogers (born 1979), who is known for her unique blend of genres and influential style.

Other notable individuals named Kelis include Kelis Kaluniko (born 1967), a Greek Olympic swimmer who competed in the 1988 and 1992 Summer Olympics, and Kelis Hendawati (born 1985), an Indonesian actress and model.