From the Semitic root ق-م-ر (q-m-r), related to the concept of the moon's pale light. Cognate with Hebrew יָרֵחַ (yareakh) in meaning, and sharing the root with Classical Arabic اِقْمَرَّ (iqmarra, "to turn pale white") — the moon being the archetypal pale, luminous object in the night sky. The same root gave rise to قَمَرِيّ (qamarī), meaning "lunar," still used in modern Arabic for the Islamic lunar calendar (التَّقْوِيم القَمَرِيّ).

The moon holds deep cultural significance across the Arab world. It is central to the Islamic calendar — Ramadan begins and ends with the sighting of the crescent moon (هِلَال, hilāl). The crescent and star symbol on many Muslim-majority national flags reflects this importance. In Classical Arabic poetry, قَمَر is also a term of endearment, used to describe someone of radiant beauty — calling someone "يا قمر" (yā qamar, "O moon!") is a heartfelt compliment still heard in everyday speech and song today.