The phrase comes from the first real-time strategy game in the franchise called Starcraft, which was first released in early 1998.
It can be heard when controlling Protoss faction units called Zealots. It literally means that these units are willing to die for “Aiur” their home world when in battle.
The real-time strategy game in the franchise called Starcraft, was released in 1998, where the phrase can be first heard and repeated, however it is impossible to tell when did the phrase first make it to the internet.
The first mention on the website called Urban Dictionary has an entry submitted by a user, explaining the meaning and use of the phrase in 2017.
Not a very popular term on the internet as its use is limited to a closed fandom of the franchise called Starcraft.
In the beginning it was mostly used in person by fans playing the game, but later on made its way to the internet and was used on fan made websites and various gaming forums, however it has gained a bump in popularity when the second full game of the franchise was released in mid-2010.