Originally, it was an online bookstore called Cadabra.
The story of how Amazon became Amazon is a prime example of how difficult the company-naming process can be. As Brad Stone writes in his 2013 bestseller, "The Everything Store," "Cadabra" was intended as a reference to the word "abracadabra" (as in, magic).
Yet Stone writes that CEO Jeff Bezos' first lawyer pointed out that the reference was too obscure. Plus, when you were on the phone, people sometimes heard "Cadaver" instead.
It was in the mid-'90s when Bezos and his then-wife, MacKenzie Tuttle, started exploring other possibilities. They registered the domain names awake.com, browse.com, and bookmall.com. They also registered the domain name relentless.com and kept it (if you type that into your browser today, you'll be redirected to amazon.com).
Bezos then started paging through the "A" section of the dictionary. At the time, website listings were alphabetized, so he wanted a word that started with "A." When he landed on the word "Amazon," the name of the largest river on the planet, he decided that was the perfect name for what would become earth's largest bookstore.