In the Avestan calendar the 9th month is that of Brightness, FIRE and August the 24th is the great fire festival in the Zoroastrian calendar.
The Avestan word for “bright fire” is áthrá/áthar. Áthrá/áthar is related to Greek Aether/Æthere “Brightness.” Also Greek aithēr from the base of aithein “to burn, shine” comes from the same root.
In Greek mythology Æthere is the personification of the upper air, the pure upper air that the gods breathe, as opposed to the normal air breathed by mortals.
In the later Avesta, the word átharxsh also appears for “brightness, fire.” The middle Iranian word átarxsh, Parthian ádar, Modern Persian ázar or átash are all derived from the old Avestan form. Kurdish Ágar is related to Vedic Ágni, ignis, “to ignite.”
Zoroastrian veneration of fire goes back to the ancient Aryan and Indo-European times, to the veneration of light, warmth, and comfort of the hearth fire. Ancient Iranians, Aryans regarded fire as the visible embodiment of the divine in material nature.
Traditionally each Zoroastrian must establish his or her own hearth fire when setting up a home. The hearth fire/light is not allowed to go out as long as the Zoroastrian person lives, and must forever burn thereafter in the line of his people or clan.
The Greeks too had a cult of the hearth fire, and although Herodotus (3.16) mentions the great veneration in which the ancient Iranians held fire, he does not single them out as being in any remarkable way “fire-worshippers,” nor does he know of temples of any kind among them (1 .131).
Herodotus states: The customs which I know the Persians to observe are the following: they have no images of the gods, no temples nor altars, and consider the use of them a sign of folly. This comes, I think, from their not believing the gods to have the same nature with men, as the Greeks imagine.
In Zoroastrianism, the promise of a mortal man is to become immortal and godlike through ma(n)zdá “passion, creativity, imagination, vision, will and mind-power.” Fire of all elements best embodies “passion, mind-energy and the will power to godhood.” Hence in Zoroastrianism, bright fire and not human-like idols symbolize the passion, and conscious energy in the universe.
Heraclitus (c. 535 BCE – c. 475 BCE) seems to have been under great Zoroastrian or Magi influence for he considered fire to be the most fundamental of all elements. He believed “All things are an interchange for fire, and fire for all things, just like goods for gold and gold for goods.”
In Zoroastrianism, religious offerings are made in presence of fire/light, holy water and sacred twigs of plants.
In the poetic gathas “mainyü áthrá-čá” is a common occurring phrase. It denotes the association between mainyü “mind-energy, passion, power of the spirit, vision” and áthrá “bright fire.”
Also in Yasna 51.9, 2nd rhymed verse line of the poetic gathas; the ancient Aryan prophet talks of a fiery molten metal before farshö-kart or the birth of a fresh new world.
The verse talks of the purifying and cleansing power of fire before the world’s end and the new birth/rising of a splendid, new creation.
I shall end this article with the inspired words of Heraclitus; “This world, which is the same for all, no one of gods or men has made. But it always was and will be: an ever-living fire, with measures of it kindling, and measures going out.”
Greek αἰθήρ is from IE root *aidh-
So that it is related Av. aēsma- “firewood”