In an earlier comment, Saemma had asked how the severe macaw got its name. I supposed that the common name came from the scientific name "Ara severa" but that's not very helpful -- where did the scientific name come from?
I did some googling around and found a book called Dictionary of Birds in the US: Scientific and Common Names by Joel Ellis Holloway. Google showed me p. 32 about the severe macaw, and here's what it said:
Ara -- part of the Tupi Indian word for macaw
Severa -- comes from Latin "severus" meaning stern, strict, or severe. Reference is to the scolding call.
Personally, I don't find the severe macaw's call to be more scolding than that of any other macaw, but interesting nonetheless!
I think this book will be very interesting as we continue with our birding, so I'm going to purchase it. I love etymology and parrot-related etymology is even better. Thanks for the interesting question, Saemma!