Well in America the word Reservation was used for land set aside for Native tribes long before the idea of a "nature' reserve ever sprang up. That's why we typi

Well in America the word Reservation was used for land set aside for Native tribes long before the idea of a "nature' reserve ever sprang up. That's why we typically use refuge for what you would call a reservation. The only reason the word reservation has a positive connotation to you is because of what it colloquially refers to in your country. It's base definition is really anything that's been reserved for a specific purpose, doesn't have to be for wildlife preservation. I doubt whoever named this facility back during WWII-era was attempting to soften up the image of it. Given that it was part of the Manhattan Project they probably didn't even think the general public would be aware of it.