The content of Columbus' personal letters and diary entries prove most revealing. One telling difference between Columbus' personal writings and those of his contemporaries was the language it was written in, namely one unrecognizable to most native Spaniards. Linguistics professor Estelle Irizarry, after analyzing the language of hundreds of similar letters concluded that it was written in Castilan Spanish or Ladino, a Jewish version of the Spanish language, analogous to what the Yiddish language is to German.
Another revelation is in the mysterious monogram found on his the letters, written right to left. To quote Semitic linguist Maurice David, who discovered the meaning of the symbols, "On all of these... intimate letters the attentive reader can plainly see at the left top corner a little monogram which is... in fact, nothing more.... than an old Hebrew greeting....frequently used among religious Jews all over the world even to this day". The symbol he was referring to were the Hebrew letters bet and heh, which we know to stand for b'ezrat Hashem, or with God's help. Not surprisingly, Columbus' letter to the King and Queen was the only one of his 13 letters studied that did not contain this symbol.Christopher Columbus, Secret Jew by Bluma Gordon [Aish.com]
There has been a lot of speculation about both his language he used (Castilian) and his use of the “mysterious monogram” which Morison covered to a significant degree in his book “Admiral of the Ocean Sea” back in 1943 for which he was awarded the Pulitzer Prize.
Castilian was the language of many seafarers of that day, somewhat of a Lingua Francas for a profession in which many men of different origins and languages were thrown together, and given Columbus’ upbringing and origins, his use of it is not only unsurprising, but expected.
As for the monogram, nobody knows, and didn’t back in 1943, though it did indeed contain an element (of the multiple elements of that “mysterious monogram”) that could be interpreted as referring to Christ.
I think the assertion is thin gruel, IMO, from a book that has a point to make to garner sales.