I couldn't find complete lyrics, but I did find an explanation of the title here:

By the end of the 15th century, comic scenes set to the folía had become a staple at popular festivals and court shows. The anonymous 16th-century Portuguese vilancete Não tragais borzeguis pretos is an example; alluding sarcastically to the dreary dress code imposed at the court of King João III, it instructs the courtier that black buskins (the laced leggings covering the lowerleg and foot) shall henceforth not be worn.

So the title NÃO TRAGAIS BORZEGUIS PRETOS translates to DON'T WEAR BLACK BUSKINS.

By the way, that web site is devoted to exploration of the many variations of "La Folía", a Portuguese folk tune that has been adapted by many composers.