It has recently come to my attention that the good deities in Zoroastrianism (Ahuras) are etymologically relayed to the evil ones in hinduism (Asura) and the inverse applies to (Daevas to Devas). It's been theorized that Zoroastur inverted the morality and cosmology of hinduism. But it seems to me that their ethics aren't even so different as to worship each other's devils. On the surface at least, it seems like they have a lot in common. Is there something I don't know about this?
But it seems to me that their ethics aren't even so different as to worship each other's devils. On the surface at least, it seems like they have a lot in common.
You have the right idea. If you just look at a handful of names and words out of context, it can start to look like Zoroastrianism and Hinduism are antagonistic, but with additional context their relationship becomes more clear.
To understand that relationship, it's important to understand Zoroastrianism's and Hinduism's shared roots. Both are derived from what linguists/anthropologists call Indo-Iranian religion, and many of their holy texts and prayers come from Indo-Iranian languages. This "Indo-Iranian" category is part of the larger "Indo-European" group of culture and languages. Beginning around 3000 BCE, a group of people from about modern Ukraine began spreading, both by physically migrating and through others adopting elements of their culture. Most of the eastward migration from those Indo-Europeans developed into the Indo-Iranians.
For a time, the Indo-Iranians were concentrated in Central Asia, but around 1700 BCE several Indo-Iranian groups began migrating south. Part of that group went east and settled in what is now northern India and Pakistan. Others went west, where they formed the ruling class of an empire called Mittani, and possibly the Kassites. These migrations are not documented, but we know from the religious language used by these groups that they shared a language. In the west, that language mostly died out, but in the east it became Sanskrit and was used to compose prayers and stories into the Vedas.
It's not entirely correct to call their religion "Hinduism" at that early point, unless you mean "any polytheistic priestly Indian religion." "Vedic Religion" eventually became part of Hinduism, but only through exposure to Dravidian elements and the philosophical revolutions of the 7th-4th Centuries BCE.
Those that remained in Central Asia continued along their own religious and linguistic development to become the "Iranians," though both they and the authors of the Vedas continued to call themselves "Ariyanem," or "Aryans" as early modern scholars often translated it. Many of them continued to practice their traditional religion and speak their traditional languages, but over time they changed to fit their Central Asian context just as their cousins in India changed too. Some Iranians even migrated westward again, where they became known as the Scythians.
Sometime around 1200 BCE, a priest in this Central Asian Iranian culture, called Zarathustra (or Zoroaster in Latin), launched a religious reform movement. The key tenants of this movement included centralization around Ahura Mazda as the supreme deity with many good suboordinates and a rejection of a collection of other gods associated with warfare and cattle rustling. The latter group were identified as daeva. Right around the same time, another wave of migrations took Iranian peoples south into modern Iran, taking Zoroastrian and Zoroastrian-like beliefs with them.
In the Vedas and Hinduism, Asura and Deva are both large categories, and specific gods are regularly identified with one or the other. However, they are also fluid. Some gods are identified as both at different times. The Asura are not necessarily "evil," so much as power hungry and the more violent and ambitious aspects of otherwise benevolent gods are called Asura right alongside consistently hostile forces.
In Zoroastrianism, Ahura is a relatively rare title. Aside from its use in the name of Ahura Mazda, it is only rarely applied to Mithra and Anahita or used in a vague sense of unidentified "Ahuras." On the other hand, Daeva are a well defined category of false and evil gods that have to be rejected. They are not fluid categories, so there is no redemption for the Daeva and the Ahuras and the other gods (called yazata) never falter. Despite the linguistic origins of the names, the "good" group and the "bad" group in both religions have broadly similar morality. Interestingly, Buddhist tradition ultimately adopted a rigid position similar to Zoroastrianism with Deva as the good category and the Asura as evil.
Early modern western academics really did use those categories to theorize that the split between Zarathustra and traditional religion was actually the impetus for the Vedic migration into India. More recent evidence has invalidated that. The archaeological and linguistic evidence makes it clear that Zarathustra lived many centuries after that split occurred.
Other evidence that the split was not caused by direct antagonism between Indian Vedic Religion and Iranian Zoroastrianism can be seen in the names of their gods. While Indra is identified as both a benevolent Deva and an evil Daeva, Mithra/Mitra is both a Deva and an Ahura. Several other gods overlap in both ways. Varuna is malevolent in the Vedas and (sort of) beloved in Zoroastrianism; Agni/Atar and Soma/Haoma are good in both, etc.
This is a fascinating question and not one I'd considered with the similarity between the opposing words. Hope to see a linguist or anthropologist chime in, but I'd imagine it's similar to how Shiva is seen in modern Hinduism.
Not a direct answer to the question, but to set some of the terms/religions used into context, "Hinduism" describes a set of religions formed in parallel with other religions such as Buddhism and Jainism from the more ancient Vedic religion where Asuras and Devas are described. Hinduism as we recognize it is certainly newer than Zoroastrianism, but the Vedic religion shares a common ancestry with Zoroastrianism (as well as the Greek and Roman religions) in the Indo-Aryan religion. See here for context:
No.
The original Indo-Iranian Religion possibly worshipped their gods with the titles Deva/Daeva and Ahura/Asura
By the time of Zarathustra, the Iranian Faith was vastly different from that of the Indo-Aryans.
Zoroastrianism was not an inversion of Hinduism as much as it is an evolution of the same ancestor. Modern Zoroastrianism is completely different from Modern Hinduism because Modern Hinduism is completely different from Vedic Hinduism, same with Modern Zoroastrianism and the Zoroastrianism of the Zarathustra.