Here's an interesting quote: "Mr. [Charles] Southwell has taken an objection to the term Atheism. We are glad he has. We have disused it a long time [...]. We disuse it, because Atheist is a worn-out word. Both the ancients and the moderns have understood by it one without God, and also without morality. Thus the term connotes more than any well-informed and earnest person accepting it ever included in it; that is, the word carries with it associations of immorality, which have been repudiated by the Atheist as seriously as by the Christian. Non-theism is a term less open to the same misunderstanding, as it implies the simple non-acceptance of the Theist's explanation of the origin and government of the world."
-- George Holyoake, 1852, introducing the term non-theism.
Also, apparently, Oxford English Dictionary says that non-theism means: "A person who is not a theist".
But if one researches the term non-theism, it's an umbrella term that includes atheism, pantheism, ignosticism, agnosticism, theological non-cognitivism, and more.