In Overlord Maruyama used to show New Worlders muck up foreign terms from YGGDRASIL. This is clear when Platinum Dragon Lord mistakes a Guild Weapon to be called a Guilty Weapon and is corrected by Rigrit in the WN. Then there is the Lair-bellup thing in the LN.

Well a theory sprang up from some info to explain why the Black Scripture was deployed to the Great Forest of Tob with all their members and a World Item when Ainz had yet to encounter anything that would warrant such a force (the Theocracy was clear several times in the WN that Godkin alone could take Dragon Lords and the Cardinals in V10 suggested the Calamity Dragon Lord did not possess Wild Magic). So what gives? Were they on their way somewhere? Was the path through the forest just a detour?

Well one theory to address this is, the Calamity Dragon Lord was Zy'tl Q'ae.

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Evidence #1: The Theocracy by LN Volume 1 had already deployed the the Black Scripture to protect their World Item to confront the awakening of the Calamity Dragon Lord, hence why the Sunlight Scripture had to assassinate Gazef Stronoff.

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Evidence #2: When people were curious when the Calamity Dragon Lord would make an appearance around Volume 4ish (December 2013), Maru said: "So you expected the Dragon Lord without any screen-time? However... is it reasonable it survived?

…It was completely destroyed/defeated in the past among other things

like-... secrets are leaking out, secrets are being exposed."

where coincidentally Volume 4's Special Edition was the one which came with the Zy'tl Q'ae Drama CD.

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Evidence #3: WN Part 2 provides the greatest support:

"In addition to a region controlled by Giants, dragons also reside [in the mountain range], there are things like that there.. "

Honestia, Jet, and Nemeru held no sign of being in wonder at those words.

"Dragons, huh. Well they do not appear in the forest. A large part of the forest around the Azellarious Mountains is segregated from the territory of the Frost Dragons so there is no need to worry. "

...

"In addition to the fact the Great Forest is enormous, it also contains a sealed being [motsu sonzai ga fuurin], those dragons will not draw near. It is seemingly said [because of] the Demon Tree Dragon Lord [Ma Ki no Ryuuou]. As this comes down from orally passed stories I've compiled and merely a few lines in a few books makes it seem that is nothing more than a baseless story. ... "

"Evil Tree Dragon Lord....should it not be a Forest Dragon?"

For something to gain renown in a forest like a dragon, Honestia's question made sense yet Fluder frowned.

"...In relation to that [question] no one can tell. Practically all the books have deteriorated to a great extent. Why they did not protect their books with magic, I seriously want to examine that person's brains!...I apologize, I got a little excited. Going back to those stories. There is no certainty that it can even be interpreted as Evil Tree. Perhaps even the word 'tree' was used incorrectly, rather it may be a dragon lord whose power relates to trees...we cannot be sure from that line if it's perhaps a dragon lord who is proficient at manipulating [ayatsuru] them like a druid magic caster. "

So what does that fudging up of names have to do with this other evidence and the Calamity Dragon Lord you might say? Well consider the following:

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Evil Tree Dragon Lord= Ma Ki no Ryuuou 魔樹の竜王

The Drama CD is called the 封印の魔樹 or the Sealed Evil/Demon Tree

Catastrophe Dragon Lord= Karamati no Ryuuou 破滅の竜王

カタストロフ・ドラゴンロード

or as he is also called:

災厄の竜王 (the nippers sometimes write the names together as "破滅（厄災）の竜王" or "Catastrophe (Calamity) Dragon Lord" )

Which is written as Saiyaku Dragon King, but you should know that Dragon King is supposed to be pronounced Dragon Lord as how Catastrophe Dragon Lord's name comes with the proper Kanji name and his Furigana Pronunciation guide. So what does that mean?

Well Saiyaku can be translated as Calamity or からまち [Ku-ra-ma-ti], which only got used once for his name. Some people think it was just Maru derping, but others think not only are they synonymous but was meant to suggest the differences in name for this Dragon Lord.

That is, まち [ma-ki]

So it's like how Le-Vel Up-> Lair-bell Up

In this case Kuro-Maki->kura-Mati

As in this Kuro is Guilty Evil Tree (rather than the black definition kuro which is also supposed to a hint from the the whole Guilty Guild mix up).

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tl;dr So basically....

Some Nipper got bored, was playing around with his kanji and trying to understand the whole Calamity Catastrophe mixup and then settled on it's NWers botching a term into something more Chuuni or edgy.