From Wikipedia (from the chapter Language)
"Phillips and Phillips point out that 500 years ago, the Latinate languages had not distanced themselves to the degree they have today. Bartolomé de las Casas in his Historia de las Indias claimed that Columbus did not know Spanish well and that he was not born in Castile. In his letters he refers to himself frequently, if cryptically, as a "foreigner." Ramón Menéndez Pidal studied the language of Columbus in 1942, suggesting that while still in Genoa, Columbus may have learned notions of Portuguese-influenced Spanish from travelers. In his business, he would have used a sort of commercial Latin as a lingua franca (latín ginobisco for Spaniards). He suggests that Columbus learned Spanish in Portugal through its use in Portugal as or "adopted language of culture" from 1450. This same Spanish is used by poets like Fernán Silveira and Joan Manuel. The first testimony of his use of Spanish is from the 1480s. Menéndez Pidal and many others detect a lot of Portuguese in his Spanish, where he mixes, for example, falar and hablar. However, Menéndez Pidal does not accept the hypothesis of a Galician origin for Columbus by noting that where Portuguese and Galician diverged, Columbus always used the Portuguese form. Even in his latest writings, he uses quero and cualquera (instead of quiero and cualquiera) in spite of the years spent in a Spanish-speaking milieu. Menéndez Pidal thinks it is probable that Columbus spoke Portuguese, while not really distinguishing it from Spanish.
Latin, on the other hand, was the language of scholarship, and here Columbus excelled. He also kept his journal in Latin, and a "secret" journal in Greek.
According to historian Professor Charles C. Merrill, adding to the fact that Columbus never wrote in Italian, not even in his letters to his brothers and bankers in Italy which were always in Spanish, analysis of his handwriting and style made by Lluis de Yzaguirre and Father Gabriel Roura indicates that it is typical of someone who was a native Catalan, and Columbus' phonetic mistakes in Spanish are "most likely" those of a Catalan. Also, he married a Portuguese noblewoman, Filipa Moniz, the daughter of Bartolomeu Perestrello who had been made first governor of Porto Santo in the Madeiras. She was also the granddaughter of Gil Moniz, who came from one of the oldest families in Portugal, and who had been a close companion of Prince Henry the Navigator. This is presented as evidence that his origin was of nobility rather than the Italian merchant class, since it was unheard of during his time for nobility to marry outside their class. This same theory suggests he was the illegitimate son of a prominent Catalan seafaring family of patricians, bankers, and merchants who sailed across the Mediterranean, the Colom, which had served as mercenaries in a sea battle against five merchant genoese vessels 10 kilometers off the coast of Portugal in 1476, as Columbus himself recognized at the end of his life, also saying that he wasn't the first Admiral of his family, an allusion to Guillaume Casenove Coulon, Commander of the corsair ship of 1476 with whom he sailed because he was his relation, as mentioned by his son and biographer Fernando Colón. When the vessel he was in got on fire, he had to jump for his life and swam two leagues to the shore, as recalled by his descendant Historian Dr. Anunciada Colón de Carvajal. Beside that, in the 19th century Italian Historian Pessagno found the list of sailors of those Genoese ships and the name of Columbus wasn't counted among them. Fighting against Ferdinand and being illegitimate were two excellent reasons for keeping his origins obscure. Adding to that, he was also a literate and learned man, versed among other things in languages, chartography, and astronomy, in a time when only aristocracy could achieve such knowledge. Furthermore, the disinterment of his brother's body shows him to be a different age, by nearly a decade, than the "Giacomo Colombo" of the Genoese family. Columbus also said that he sailed since a very young age, which suggests a link to a family of seaman, in opposition to the Italian Columbus, who only became a sailor at around age twenty."
For more reviews from my travels, see www.operaduetstravel.com