Christopher Columbus is from the second half of the 15th century and the early years of the 16th century, a time when it was common for names to be translated or adapted into the different languages, more or less the same as it still happens with royal names nowadays in some countries (in Spain, for example, you'll find the news about king Charles III of the United Kingdom talking about "Carlos III").

The first Admiral of the Indies is a very interesting example, as the paper trail about the man shows quite some different names:

In the year 1476 he participated in a commercial expedition to the island of Madeira for the Centurioni company for which he was working. The deal did not go quite as right as planned, and this resulted in a lawsuit, of which we have the verbal thanks to notary Ventimiglia, who took part in it. In that suit, we see the name "Cristoforus Columbus", with the obvious legal indication of "cives Janue".

The first reference we have about Columbus in the realms of what today is Spain is a note of payment for a certain sum of maravedis by order of Alonso de Quintanilla. In that document, the name appears as "Xpoval de Colomo", and the indication "extrangero". A transcription developing the abbreviations would be "Christoval de Colomo", probably because the treasurer misheard "Colombo", which would not be unusual.

In later documents we see Columbus with the name we known him by in Spain: Xpoval Colon, or "Christoval Colon" if we develop the abbreviation, which in correct modern Spanish orthography is Cristóbal Colón. That's the name he seems to have used in Castile, or at least that is what the records show. The "Short registry" by doctor Lorenzo Galíndez de Carvajal, who was registrar of the Royal Court, contains an indication in the year 1491 saying "tuvieron asiento Sus Altezas con Christoval Colon, ginobes, natural de la Saona[...]", which translates as "Their Highnesses had audience with Christopher Columbus, Genoan, natural of Saona".

In 1493, right after coming back from his first journey, the Admiral met the king of Portugal, who sent a letter to the Catholic Monarchs saying that their Admiral "Xpovao Colombo" had safely arrived in Lisbon, and that he would be on his way as soon as possible.

In the year 1501, Columbus became friends with Anzolo Trevisan, secretary to the Venetian ambassador before the Catholic Monarchs, and Trevisan was allowed to copy some of Columbus letters. In the beginning of one of the letter we can read "Cristoforo Columbo, zenouese, homo di alta et procera statura, rosso, di grande inzegno", meaning "Christopher Columbus, Genoan, man of tall and remarkable height, redhead, of great ingenuity".

So, in the Admiral's own time, in documents closely linked to him we have quite a number of different forms: Christoforus Columbus, Cristoforo Columbo, Christoval de Colomo, Christovao Colombo, and Christoval Colon.

As I said earlier, it was a perfectly ordinary practice to adapt names into the different languages, and the cases are not exactly in short supply. Case in point from the mid 16th century, the Spanish theologian and writer Francisco de Enzinas: in his matriculation registry at the university of Leuven he is listed as "Franciscus Densines, Hispanus", in his letters he signs as "Franciscus Dryander", in Spanish documents he is "Francisco de Enzinas", and in the French translation of his book "De Statu Belgico deque Religione Hispanica" he is "Françoys du Chesne, espaignol".