The name Alonzo originated from the Spanish and Portuguese languages, derived from the ancient Germanic name Alfonso. Alfonso itself is a compound of the Germanic elements "alf" meaning "elf" and "funso" meaning "ready for battle" or "eager for combat."

The name Alonzo gained popularity during the Middle Ages, particularly in the regions of Spain and Portugal where it was widely used among the nobility and ruling classes. It is believed to have been introduced to the Iberian Peninsula by the Visigoths, a Germanic tribe that ruled parts of Spain and Portugal from the 5th to the 8th centuries.

One of the earliest recorded instances of the name Alonzo can be found in the 9th century, when it was borne by Alfonso II, a king of Asturias in northern Spain who reigned from 791 to 842. Another notable historical figure with this name was Alfonso X, also known as Alfonso the Wise, who was the King of Castile and León from 1252 to 1284. Alfonso X was a renowned patron of the arts and sciences, and his court was a center of learning and cultural advancement during his reign.

In the 11th century, the name Alonzo spread beyond the Iberian Peninsula and gained popularity in other parts of Europe. One of the most famous bearers of this name was Alonso de Ojeda, a Spanish explorer and navigator who accompanied Christopher Columbus on his second voyage to the Americas in 1493. Ojeda later led his own expeditions and played a significant role in the early Spanish exploration and colonization of the Caribbean and South America.

Another notable figure named Alonzo was Alonso de Ercilla y Zúñiga, a Spanish soldier and poet who lived during the 16th century. Ercilla is best known for his epic poem "La Araucana," which chronicles the Spanish conquest of Chile and the resistance of the indigenous Mapuche people.

In the realm of literature, one of the most famous characters named Alonzo is found in John Milton's epic poem "Paradise Lost." Alonzo is one of the fallen angels who follows Satan in his rebellion against God.

Through the ages, the name Alonzo has maintained its connection to Spanish and Portuguese cultures, although it has also gained popularity in other parts of the world, particularly in the Americas due to Spanish and Portuguese influences.