Why is Montgó called Montgó ?.

Well, take your pick from the following account which has been translated from the Spanish and adapted by Joan Franklin:
Source: an article by Roc Chabas, a historian of Dénia who wrote in 1856 as quoted in "Parque Natural del Montgo - Estudio Multidisciplinar" - Valencia: Conselleria d'Administració Pública, Agencia del Mediambient. 1990

There are many versions of the etymology of the word "Mongo" or Montgo, most of them invented:

1. It is derived from Magon, a Carthaginian captain, but there is no evidence that he ever came to Dénia (not even from his most passionate devotee ! says Chabas).
2. There are other that say it is derived from the Greek word "Monokos", which means "unique and eminent". Chabas dismisses this by saying: "If this word were not also a proper name, it might have been so- called by the appearance of the mountain, but as it is also a proper name, this theory is called in to doubt."
3. Others are of the opinion that the sages who founded Dénia called it Mons Sagon. The "s" was lost and it became Monsagon, and later Mongon and Mongó. Chabas doesn't like this either because, he says "it assumes that there were such people as the sages who founded Dénia and there is nothing to indicate that; and secondly, it would also mean that these sages spoke Latin."
4. The opinion of a Father Pedro Esteve was that the name came from "Mont-goy" (the word "goy" in Hebrew meaning non-Jewish), and "Mont-goy" therefore meant the "mont de gent" or "mont de gentilidad" - meaning the mountain of the gentiles. Chabas thinks this meaning is much more probable than the others as there were so many Jews in Spain in the earlier centuries.
5. Then along comes someone called P. Diago who said the name derives from Mons Jovis - because of its "extreme height" (sic) it was dedicated to Jupiter. The name later became Monjó, and then Montgó.
6. To settle these arguments and theories Chabas says that his opinion of the name is not supposition but history, and that it is derived from Mont Caon. He says there is no doubt that it was thus called in the 10th Century, because an Arab author wrote of the plants which were growing on the slopes of Caon.

He says that the change from Mont Caon to Montgó was easily explained by the dropping of the letter "t" in Mont, the "c" becomes "g", and the dipthong "ao" becomes "o"

So now we all know....that explains everything doesn't it? (except...what does "Caon" mean- Ed)