The red grape variety originates from Portugal. Synonyms grouped alphabetically by country are Sousao, Souzao (California); Espadeiro Basto, Espadeiro da Tinta, Espadeiro de Basto, Espadeiro Preto, Negrão, Negrão pe de Perdiz, Pinhão, Sousão, Sousão de Correr, Sousão Forte, Souzão, Souzão Forte, Tinta Nacional, Tinto Antigo, Tinto de Parada, Tinto Nacional (Portugal); Azal Tinto, Caíño Gordo, Loureira Tinta, Negron, Pazao, Retinto, Sousón, Sousón Retinto, Tinta de Luzin, Tinta País, Tintilla, Vinon (Spain). The parentage (parentage) is unknown, but some DNA analyses brought important insights. The varieties Sezao (Sousão) and Vinhão are probably identical. There is a parent-offspring relationship with the often confused variety Amaral. The variety Padeiro originates from a presumably natural crossing Hebén x Vinhão. Under the name Sousão, Vinhão was the crossing partner of the new variety Argaman. The grape variety picture comes from the work "Ampélographie - Traité général de viticulture" by Victor Vermorel and Pierre Viala, published in 1910.