[1] The use of the term can be traced, according to current knowledge, to the beginning of the 13th century in northwestern Portugal.
[1] The historical writing form of the term Vieira was Vyeyra.
[1] As a surname, the term is first found in northwestern Portugal in the province of Minho in the era of Kings D. Afonso II and D. Sancho II of Portugal around 1220 A.D.[1] The historically common spelling Vyeyra is still found at least until the end of the Middle Ages in the mid-16th century.
At least until the end of the Middle Ages, the use of the letter Y (y) was still common in Portuguese written language, as illustrated, for example, by the following text from the 16th century:... toda junta a quinze dyas de aguosto hou se o tempo que lhe pareçese bem he menos pryguo se espera se lhe fezese faroll da sua naao he pelo pomto do seu pyloto vyese demandar guoa he ele com hos guoleons que fiquavam hatravesase a jmdea pare-.
ceu a todos bem he cheguado a naao do fejtor perto do gualeom do gouernador foy hele la em hũ esquyfe a quem deu ho Regymento da maneyra que comprya mais a servyço d ell rej noso senhor he alem deste mandado ha que as fustas provese dese fresquo ho mais que lhe fose necesaryo a quall despedyo de sy ho mesmo dya ja noyte he sy a nau de jorge vyeyra merquador em que levaram consyguo da jmdea quareguada de manty- mentos ha armada com lycença ha hurmuz he hũs na vollta da serra he outros na vollta do mar desapareçerom ...[4]Regarding the term Vieira, the writing with the letter I (i) instead of the Y (y) has basically become established.