There are many theories about Machu Picchu, but some theories are backed by more research than others. Paolo Greer, Inca investigator/historian, and personal friend of mine discovered the first map ever drawn of Machu Picchu. The map that was drawn by Hermann Gohring in 1873 and printed in 1877, 50 years before Hiram Bingham ¨discovered¨ Machu Picchu. The map also indicates that the site we now call "Machu Picchu" was actually called "Patallacta", "Wayna Picchu" was labeled as "Machu Picchu", and "Putucusi" was labeled as "Wayna Picchu".
Why are these names important, well "Patallacta" in quechua means "High City" which makes sense since Machu Picchu is a high city.. The map showed "Wayna Picchu" labeled as "Machu Picchu", Macchu Picchu is quechua for "Old Mountain", this also makes sense since Wayna Picchu is the mountain looking down on MP. The 3rd. mountain, "Putucusi" was labeled as "Wayna Picchu" quechua for "Young Peak". Somehow the names all got all mixed and they will most likely stay the way they are now.
If you are interested, I have added extra bits of info with each photo as well, just click on the photo to read more.