Cebollón is a playful augmentative of "cebolla" (onion), literally meaning "big onion." In the context of this corrido, it's used as a nickname for one of the main characters.
Nicknames are very common in Mexican culture, especially in corridos, and often reflect a person's characteristics, origin, or even a humorous anecdote. This word is interesting because it's not a standard dictionary term for a person, making it unique and memorable in the song.
This corrido, "El Compa Cebollo," tells the story of Pedro Mojarro, also known as "El Cebollo." The song begins by setting the scene in the "Petaca de los Chivos medio del valle del Yaqui" [Goat's Suitcase in the middle of the Yaqui Valley], where Pedro grew up. He started making a name for himself at 17, traveling between Sudan and California.
The lyrics celebrate his success, noting that "Ahora todo es diferente hay billetes para gastar" [Now everything is different, there's money to spend]. Despite his wealth, he's described as a "persona muy humilde" [very humble person] who helps his community. The song also gives a shout-out to his friends in Nayarit, and ends with El Cebollo heading back to his ranch, ready to celebrate with music!