Where does "gringo" word from?

There are many theories about the name of “gringo”, the oldest version comes from Roman times and his Latin proverb “graecum est; non potesti legi”, meaning of “is in Greek, can’t be read”. This phrase has been used in many European countries and persons, such as Shakespeare: “It’s all greek to me” (Julius Cesar).

In addition, it’s interesting to know that the gospels were written on greek before latin. However, some historians believe in the association to “greek” with “foreigner” to indicate that the greek language wasn’t necessary to understand the holy scriptures.

Moreover, “gringo” word appear written on Spanish XVIII c. in the famous “Diccionario Castellano”(1786-1793) researched by father Esteban de Terreros y Pando, explaining that the word was used to refeer someone (foreign) who speak Spanish with difficulties.

In other hand, “gringo” word could be a transformation of the word “greek” because “gringo” word appears on RAE (Royal Spanish Academy) first time in the year 1869 and was defined: “familiarly voice used. Also used as a greek in this phrase: talk in gringo, doing it on a language unintelligible”.