<= Has degree in linguistics.
The etymology of the word atheist ("not a theist"), unfortunately, will not resolve the arguments that happen every time the precise meaning of "atheist" is debated. Which is why if you read up on atheism, you'll find that there are all kinds of hair-splitting distinctions between agnostics and atheists, both of which are classified on a "weak/strong" axis.
I'm content to call myself an atheist, but technically I am a "weak atheist" (a term I don't like because while "strong/weak" is a specific philosophical term referring to the form of a hypothesis which one adopts, the implication most people read into it is "not really sure about your atheism," which is not true).
To put it simply, what most people think of as "agnosticism" is really atheism, and most agnostics are actually atheists who just don't want to call themselves that because they've been convinced of the fallacy that "atheists are asserting as an absolute proven statement of fact that there is no god." Which is only true of "strong atheists," and even they will not use the word "absolute."
What made you guys atheists/nonbelievers? (Just curious to know.)
I grew up Christian. Unlike a lot of ex-Christian atheists, my churches were not abusive or dogmatic and I don't have bad memories of them. But about the time I was a teenager, I looked around at the big sanctuary with the modern sound system and the lights and all the pretty trappings, and the Sunday school classes and the youth groups and singles gatherings and church camps and so on that the church, like most such churches, hosts, and realized that I had never actually felt a single spark of divine/supernatural presence (and it wasn't from lack of trying), and that I only believed because I thought the idea of a benevolent omnipotent deity who loves all of us is a nice thing to believe in.
And I was pretty sure that almost everyone else who goes to church feels the same way, at least outside of evangelical circles. Oh sure, in some abstract way they believe in God and Jesus and maybe there were some miracles way back when, but nobody
really believes in a non-material world. It's just a comforting thing they tell themselves they believe in because death being a big blank nothing is scary to a lot of people. It has no actual impact on their lives, their decisions, or their worldview.
Moreover, for the most part, they did not choose it as a result of any sort of soul-searching or an objective evaluation of all the available theologies whereby they chose the one that seemed most true and logical. They believe in whatever church they were raised in, or the one where they most liked the people when they went "church-shopping."
That second part is the other realization that gnawed away my faith as a teen. Religion doesn't actually change anyone's behavior. Nobody chooses not to do something they'd rather do, especially if it's something that doesn't
feel wrong to them, because they think God doesn't want them to do it. They either construct a justification for why it's okay for them to do it, or they do it anyway and feel guilty about it so they pray for forgiveness. Likewise, believers don't do things that
seem wrong to them. Whatever they think is wrong, they are convinced God also thinks is wrong. This convenient correspondence between an individual's morality and God's morality is almost universal across all religions.
For the most part, I think of believers of the non-fundamentalist sort as well-intentioned people who are generally very nice, and who would be just as nice if they were atheists. Likewise, the asshole believers would be just as obnoxious as non-believers. I have seen people convert from atheist to religious, and from religious to atheism, but I've never seen anyone who became a nicer or less nice person, or more or less moral, as a result of the conversion, either way.
The realization that religion was all a game of "let's pretend" and that even among those who actually believe in it, it doesn't affect behavior, is how I left it, realizing it neither made sense nor was it necessary.