According to the WordReference dictionary, atheism means "the doctrine or belief that there is no God or the existence of a supreme being or beings."
According to the Etymology Dictionary the word atheism was created in France in 1580 and comes from Greek a- "no" + -theos "god".
Other words referring to a- are: Amorphous, Abnormal and Achromatic. Referring to -theos are: Autotheism, Pantheism and Polytheism.
We can see the use of the word atheism in this article.