Why and when did Alberico Vespucci change his first name into Amerigo?

In 1886, Jules Marcou said Vespucci renamed himself from Alberigo Vespucci (Albericus Vespucius) to Amerigo Vespucci after meeting the native inhabitants of the eponymous Amerrique mountain ranges of Nicaragua that connect North America and South America, an important geographic feature of New World maps and charts.

https://en.wikipedia.org/wiki/American_(word)

Jules Marcou was a geologist rather than a historian. https://en.wikipedia.org/wiki/Jules_Marcou That mention in Wikipedia has been tagged as needing a proper reference since June 2007. (Which means no-one has managed to find one - it'll probably get deleted before long or altered to reflect the dubious nature of the claim.) Marcou's sources for his comment are not certain (at least to me) and many refer to this idea as starting with him. http://www.answerbag.com/q_view/679667 et al

If you look at http://books.google.co.uk/books?id=oRTK2r-TvDEC&pg=PA21&lpg=PA21&dq=%22alberico%22+amerigo+vespucci&source=bl&ots=xpiXt5vIqb&sig=oXEDSLF2lrN8f5cSFwlyn6x-Tbs&hl=en&ei=vHTvSbnNDMnOjAfH-6kR&sa=X&oi=book_result&ct=result&resnum=2 (...why do they do this?) his name can be (and was) spelled in quite a few ways - like Shakespeare and many others in the good old days before computer records... He may not have changed his name at all. The people writing about him did it for him. (Even with a nice new computer system installed, you should see some of the stuff that comes from the office to me...)