The given name Cornelio is derived from the Roman family name Cornelius, which has its origins in the Latin word "cornu", meaning "horn". The name Cornelius was borne by several distinguished ancient Roman families, including the Cornelii Lentuli, Cornelii Cethegi, and Cornelii Dolabellae.

Cornelio first gained prominence in ancient Rome, where it was associated with several notable historical figures. One of the earliest and most famous bearers of the name was Publius Cornelius Scipio Africanus (236-183 BC), a Roman general and statesman who defeated Hannibal during the Second Punic War. Another notable figure was Cornelius Nepos (c. 100-24 BC), a Roman biographer and historian.

In the early Christian era, the name Cornelio was borne by Cornelius the Centurion, a Roman centurion who is mentioned in the Acts of the Apostles as being among the first Gentile converts to Christianity. This association with early Christianity likely contributed to the name's enduring popularity throughout the medieval and Renaissance periods.

During the Middle Ages, several individuals named Cornelio left their mark on history. Cornelio Desiderio (c. 1135-1182) was an Italian Benedictine monk and author, known for his writings on theology and philosophy. Cornelio Vitelli (c. 1460-1511) was an Italian Renaissance humanist scholar and military leader.

In the early modern period, Cornelio Musso (1511-1574) was an Italian Catholic bishop and renowned preacher, who served as the Bishop of Bitonto. Another notable figure was Cornelio Bentivogli (1668-1739), an Italian painter and engraver active in the Baroque period.

As the name spread across Europe, it was adapted to various linguistic and cultural contexts. For instance, in Spanish-speaking regions, the name took the form of Cornelio, while in Portuguese-speaking areas, it became Cornélio. Notable bearers of the name in these contexts include Cornelio Saavedra Rodrigo (1759-1829), a Spanish military officer and statesman, and Cornélio Pires (1884-1958), a Brazilian journalist and writer.