Porteño Spanish is the dialect of caste-sha-no (castellano) spoken in Buenos Aires, Argentina and the surrounding areas. It is categorized by an Italian-like pronunciation and colorful Lunfardo slang.Browse Slang Dictionary
This word is popular said to have derived from the name of the legendary Gauchito Gil. His fill name is Antonio Mamerto Gil Núñez, born in the 1840's near Mercedes, Corrientes.
He was the lover a rich widow who was chased out of town by her jealous brothers. He later joined the Argentine army and fought in the war against Paraguay. After fighting the war, he was drafted in the Argentine Civil War which he deserted to become a Robin Hood-like thief.
After his capture and execution he is said to have performed several miracles and for that reason is a folkloric saint, though without recognition from the Catholic Church. His popularity is mostly in the provinces of Formosa, Corrientes, Chaco, the north of Santa Fe.
It is not clear from his legend why "gil" came to refer to "silly" or "foolish" people. An alternative etymology suggests that in fact "gil" comes from the Caló or Iberian Gypsy word "jili" which means "innocent". "Jili" is also the basis for the Spanish slang term "gilipollas" (which means "asshole" or "fuck"). It is likely that both the legend of Gauchito Gil and "jili" are the shared origin.