In early ancient Greek, the adjective atheos (ἄθεος, from the privative ἀ- + θεός "god") meant "godless". It was first used as a term of censure roughly meaning "ungodly" or "impious". In the 5th century BCE, the word began to indicate more-intentional, active godlessness in the sense of "severing relations with the gods" or "denying the gods", instead of the earlier meaning of "impious". The term ἀσεβής (asebēs) then came to be applied against those who impiously denied or disrespected the local gods, even if they believed in other gods. Modern translations of classical texts sometimes render atheos as "atheistic". As an abstract noun, there was also ἀθεότης (atheotēs), "atheism". Cicero transliterated the Greek word into the Latin atheos. The term found frequent use in the debate between early Christians and Hellenists, with each side attributing it, in the pejorative sense, to the other.
In English, the term atheism was derived from the French athéisme in about 1587. The term atheist (from Fr. athée), in the sense of "one who denies or disbelieves the existence of God", predates atheism in English, being first attested in about 1571. Atheist as a label of practical godlessness was used at least as early as 1577. Related words emerged later: deist in 1621, theist in 1662; theism in 1678; and deism in 1682. Deism and theism changed meanings slightly around 1700, due to the influence of atheism; deism was originally used as a synonym for today's theism, but came to denote a separate philosophical doctrine.
Karen Armstrong writes that "During the sixteenth and seventeenth centuries, the word 'atheist' was still reserved exclusively for polemic ... The term 'atheist' was an insult. Nobody would have dreamed of calling himself an atheist". Atheism was first used to describe a self-avowed belief in late 18th-century Europe, specifically denoting disbelief in the monotheistic Abrahamic god. In the 20th century, globalization contributed to the expansion of the term to refer to disbelief in all deities, though it remains common in Western society to describe atheism as simply "disbelief in God".
