kind of fascinating that a linguist doesn't find meaning in a predetermined being choosing their own name and purpose entirely separate from what they were meant to be
I think part of what makes Priestess so effective as Arknights' ultimate antagonist is that there's nothing significant to her on Terra. She finds the actions of Theresa and Theresis and the countless people who oppose her as nothing more than a novelty, an interesting little bug to momentarily observe before squashing it. She's threatening but not as some kind of evil overlord that wishes everything to suffer, but more of a bored god looking down on Terra and annoyed that these primitive, tiny, stupid little beings don't just listen to her and do as she says, don't they realize that she knows what's best for them?
There's a detached feeling to all of Priestess' interactions on Terra, her opponents aren't threatening, they're just a child throwing a temper tantrum because they don't eat their (Originum) veggies. It's particularly frustrating for Priestess because she's done this same song and dance of humoring newborn civilizations an uncountable amount of time to where, in her own words, she lost the enjoyment in it.
The life on Terra, the Teekaz and the Ancients and the Elders, all of them were just a random accident, an experimental anomaly that isn't offensive on its own, just another one in a million random chance that sprung up.
And yet they did something that not a single member of Oracle and Priestess' cosmic, nigh-omniscient race could. Something that eventually befell every civilization they'd encountered prior, yet Terra has seemingly circumvented.
They evolved beyond what was fated for them.
I thought at the time it was a little weird for them to continuously bring up the flower field that Theresa made with Originum during the Babel event, but the new context we have for it makes it clear why Oracle was so enraptured by it: Theresa evolved Originum in a way that Oracle never realized was possible.
Despite Oracle's misgivings and the guilt they felt over how Originum was harming a newborn civilization, this same newborn civilization with the iota of time given to them compared to the countless eons of Oracle's own civilization and technology, managed to surpass them.
Terra took Originum, the literal fire and language of the gods, and made Arts with it.
Arts, of course, has a huge double meaning here both in-context and thematically, Arts of course refer to the literal arts that people can devote themselves to and it's why so many instruments/wands/etc have a huge variety among the weapons in Terra, people cast Arts through a variety of creative means like music, writing, painting, you name it. Arknights places a heavy emphasis on the importance of self-expression to the point where it's a literal hard counter to things like Daemon infection or Seaborn assimilation, but I think looking at this in-context is also important.
Originum is fundamentally a language. While the Assimilated Universe and the actual rocks themselves serve as a storage system for the information of everything that has ever existed, that's mostly a lot of bells and whistles for what Originum really serves to do: Universal translation and understanding.
Languages are born from a primary need for communication, which is so broad that it makes sense why Originum also needs to store an absurdly broad amount of information. We even see in the beginning of Ch15 that Raydistorter has a few sequences of calibrating itself to then properly communicate with Hierda because it's combing through all the accumulated knowledge of Originum to approximate the language and means of communication that Hierda uses. This makes sense because languages are also a form of culture (civilization), they can evolve on the spot from seemingly anything like slang and memes (hell just consider Tumblr itself, phrases like blorbo and oh worm and the like, these are all memes, units of culture that become part of Tumblr's 'language' that we understand but other websites might not), so Originum stores a functionally infinite amount of information to cross reference and approximate any new culture and language it comes across.
Originum thus has a by-design need to be stagnant as opposed to ever evolving, a Rosetta Stone for any form of language it can come across.
And yet, Terra evolved it still, because the arts are still a form of communication. By nature of Originum being a language, it is still capable of the evolution any language can undergo: Cross-culture idea mixing and remixing, songs, paintings, theater, puns, memes, these are all things that can emerge from any sort of language, forms of self-expression that, in a lot of ways, go beyond language.
To Terra, the Arts derived from Originum are a form of self expression, a way to evolve beyond the static nature of a singular universal, unchanging language. A way to continually evolve language and communication. Theresa in severing the thread of fate that bound Terra's fate to Originum is also what lets them evolve beyond a set meaning.
To Priestess? Priestess literally does not care for the Arts. She does not recognize any significance in something as small as changing a name.