The rest of the story
Truth is, around that time I'd been playing the domain name speculation game for a while, and had a portfolio of about 50 domain names. When Justin and I were looking for a name, we looked at my list, and habitablezone.com kinda leapt off the page.
Basically, then, the name came about almost by accident. If I hadn't had the name already we probably wouldn't have thought of it, and would've picked another name. How about monsveneris.com? It's probably a blessing that habitablezone.com was on that list.