In the Middle Ages, flourishing period for Galician, the language was used to write poetry and literary, administrative, legal and religious prose.
Galician language between the 8th and 12th centuries
During the emergency of the Christian kingdoms on the time of Reconquista, Galicia formed a political unity with Asturias and León, with the exception of the reigns of Don García (1065) an Afonso Raimúndez (1111). Despite this dependence, nobility, church and all the Galician monasteries enjoyed power. This situation combined with the fact of the importance of Santiago as a renowned cultural and religious place allowed the development of Galician in writing only alternating with Latin.
Galician, literary language (from the 12th to the 15th centuries)
The socio-political conditions given from the 12th century allowed the acclimatisation of troubadour poetry in Galicia. At that time Galicia became the main language of lyric poetry in the entire Peninsula. Our language sounded in the voice of the troubadours and in all the royal courts of Spain. There were many poets outside of Galicia who adopted Galician as the language of poetry.
The miracle story is a widely spread literary genre in Europe during the Middle Ages. It played its role as a propaganda tool and it also had a devout function. One of the most important collections of Marian miracles in Europe is contained within the Cantigas de Santa María (Canticles of Holy Mary) by Afonso X o Sabio (‘The Wise’). In addition to their undoubted musical value, they are a monumental linguistic evidence to understand the flourishing of Galician in this moment.
The great themes of the European literature in that moment had an effect in the Medieval Galician Prose. It could be read in Galician language the books on the adventures of the Knights of Round Table, the History of Troy, the Compilation of Santiago’s Miracles, the Universal History and the History of Spain but all this literary production did not continue due to the socio-political context of the 15th century.
Galician language in social life (from the 13th to the 15th centuries)
Galician language was the oral language of all segments of the population. It was also the written language in notarial, judicial and administrative acts. Galician language was used to write administrative prose (regulations of fishermen guilds and other kind of guilds, books of minutes), notarial prose (agreements, wills or account books), legal prose (legal actions, lawsuits or translations of legal books), scientific prose (Tratado de albeitaría —a book about horse care—) and religious prose (sermons, pious reading).
It is also certainly true that Castilian language is introduced to write documents at court from the middle of the 13th century —during the reign of Fernando III.