I wonder how they arrived at the name "Ebrietas"? Does it have something to do with being inebriated?

EDIT: it does, I just had to google "Ebrietas latin" (and got https://en.wiktionary.org/wiki/ebrietas), otherwise it only returned references to the monster.

From what I recall there is a relationship in the game of how much blood you take from an outer being like her & how crazy (drunk?) the user then becomes, before becoming a crazed beast.

There is one key item in the game called “Eyes of a blood-drunk hunter”

It's designed after a moth species.

Probably more likely related to the Mexican moth, considering the character designs.