The only free and comprehensive online etymological dictionary of the Spanish language
giro (2) (Adjective) (Andalusia, Murcia, Canary Islands & Latin America) (of a rooster's plumage) "dark color;" (Chile, Colombia & Peru) (of a rooster's plumage) "spangled black and white;" (rare) "gallant"
The old meaning of "gallant" is first attested in 1734 while the meanings of cockerel colors are found starting in the 19th cent. Use of the word to mean "scar" or "facial injury" is found in a document from 1640. Of unknown origin.