Etymology of Khaenriah, and how they are demonized in Sumeru

 According to Dontreusenames, Khaenri’ah came from the Arabic word خائنرياح (ḵāʔinriyāḥ, “betrayer of winds”) → ‎خائن (ḵāʔin, "betrayer, traitor") + رياح (riyāḥ, “winds”). Now I'm here to substantiate that.

Most people see “winds” and think of Barbatos, but Istaroth actually fits better. Why? Istaroth is the god of time and is also known as “The Thousand Winds of Time.”

This is also corroborated by one of the definitions of Dahri, Sumeru's term for Khaenri’ah. Dahri comes from the Arabic word دَهْرِيّ‎ (dahriyy), which refers to three kinds of people:

people who believe that there is no god

people who believe that the universe exists eternally (i.e. it’s not created by a god)

people who believe in Zurvan, the Zoroastrian God of Time1

In the context of Genshin, the first two definitions can be summarized into one word: “heretic.” From the perspective of Celestia, Khaenri'ahns sure are heretics. If the Second Who Came is the current Celestia, then the third definition may also be heretical. This makes the Gate to Khaenri’ah being in Hangeh Afrasiyab fit so well.

Hangeh Afrasiyab is from the Persian term هنگه افراسياب (hange afrāsiyāb, "cave of Afrāsiyāb"). Afrāsiyāb is the mythical hero king of Turan, which is the country of the enemies of Zoroastrianism. Therefore in the context of Genshin, Afrāsiyāb refers the Hero King of the Heretics, King Irmin.

Not only are they heretics, but they're also demonized. Hangeh Afrasiyab is in a subarea called Gate of Zulqarnain. Zulqarnain is from the Arabic name ذُو ٱلْقَرْنَيْن (Ḏū l-Qarnayn, "Two-horned"). He is a character in the Quran that built a wall with Gog and Magog (Ya'juj and Majuj respectively in the Quran) on one side and the rest of the world on the other.

So putting all these together, Khaenri’ahns used to worship Istaroth, but stopped before adopting the name. When exactly? Well, this goes into speculation. Since Khaenri’ah prided itself to be a godless nation, they must have stopped worshipping Istaroth from the very foundation of their nation.

As for why they are then called heretics and demons in Sumeru, maybe even in the rest of Teyvat. There are many possibilities. One is that they had an energy crisis and tried to use Celestial energy and Abyssal energy to create perpetual motion machines2. In their attempts to control Abyssal Energy, Khaenri'ah accidentally causes the Cataclysm, making Celestia curse them.