El Tema del Peru

[Aka Tavy]

Is there any definitive answer as to the origin of the word Andes? I've come across information stating that it is from an indigenous word whose origin has now been lost and also a competing argument that it comes from the spanish word andinas or andines (Of this, all I have found is andinas means "related to the Andes (plural)" and andines is the French cognate of the same). The argument for this etymology is that the conquistadors, upon seeing the Incan terraces built up the mountainsides, named them after such. However, there is no such word in Spanish. Thoughts?