Kukulkán is regarded as an early Meso-American god that was known by the Mayans and Incas (and possibly as early as the Olmecs), and was also known by the Aztecs and Toltecs as as Quetzalcoatl (generally translated as: "plumed" or "feathered serpent"), Viracocha from the Peruvian legends, and Gukumatz by the K'iche' group of Maya.
In the historic-mythologic document: the "Popol Vuh", that is assumed to have been written around 3100 BC by the Maya of Guatamala, Gukumatz was described as: white skinned, caucasian-like, bearded, very tall, having a long skull, and arrived in a "cosmic boat" (spaceship?), accompanied by giant "African-like" warriors. During the time of the Spanish conquest, the natives described him to the Spaniards as a man with a white beard wearing a white robe.
To the American native indians it was common practice to often name people to certain animals, thus of course he was not a real serpent. Maybe he was called the "feathered serpent" by the Aztecs because of his supposedly white hair and beard, and his unusual head gear. Facial hair was not known of by these natives and maybe they never saw something like it, thus they might have associate his white facial hair with feathers. It might be that his beard to them looked like the tongue of a serpent, and maybe he also wore a helmet which to them looked pretty much like the head of a serpent. In ancient times the serpent was the symbol for wisdom and Kukulkán/Quetzalcoatl was remembered by the ancients as a leader and a bringer of civilization, knowledge and wisdom.
According to the book: "The Mayan Prophecies" (1995), by Adrian Gilbert and Maurice Cotterell, Kukulkán was forced to flee to the east because of a certain conflict where would have left the Maya people with the promise that he would return some day. Because it had long before been prophetized that Kukulkán would return in the year with the name "1 reed", both the Maya and their enemies: the Aztecs, who still had been sacrificing ten-thousands of people every year, believed that it was the righteous Kukulkán who had returned when the Spanish conquest took place in the year 1519.
This conquest was led by Hernán
Cortés, who believed that these people were some kind of devil
worshippers because of their bloody human sacrifices, who had to be
forcefully turned to the Catholic belief. As a result of this, most
of the books of the indigenous people were burned and most of the
ancient legends and knowlegde eventually was lost.
The priest Don Ramon de Ordoñez y Aguilar examined the site of Palenque in the year 1773, and wrote about the earliest discriptions of the ruins in his work: "A History of the Creation of Heaven and Earth", which he referred to Palenque as the great city of Nachan ("City of Snakes"). He argued that Palenque had been build by people who arrived overseas by the Atlantic Ocean and were lead by a man called Votan, who had a serpent as his symbol. The story about Votan originally appeared in a book from the early K'iche' group of Maya which had been partly copied by the bishop Nuñes de la Vega before he burned the book in the year 1691. According to the remaining copied text, Votan came into America with his people who wore long garments. The indigenous people welcomed him and subjected to his leadership and the strangers married with their daughters.
Votan would travel four times back and forth over the Atlantic Ocean to his old home, named "Valum Chivim", which Ordoñez believed to be Phoenician Tripoli (in Lebanon) and that Votan would be a Phoenician sea traveler. In chapter 4 of his book "Atlantis: The Antediluvian World" (1882), Ignatius Donneley suggested that Votan built Palenque and that "Valum-Votan" may have been a reference to Atlantis. He also noted that the character of Votan is similar to the Germanic god Wotan, and the Norse god Odin, thus possibly were one and the same person. Lewis Spence also associated Votan with the Atlantis legend in his book "Atlantis in America" (1925), where he identified the name Votan as a local name for Quetzalcoatl.