Does anyone have an idea for a name for a demon(Tiefling), They're gonna be in a comedy based story loosely based on D&D, it's supposed to be making fun of common fantasy tropes.

Walter

Some of the naming conventions for tieflings in D&D is virtue names ("Patience", "Honor", "Valiance"), so you could try those. What's the personality of the tiefling?

https://www.fantasynamegenerators.com/demon_names.php
https://www.fantasynamegenerators.com/fantasy-surnames.php
https://www.fantasynamegenerators.com/dnd-tiefling-names.php (an excerpt from this website: "Some tieflings choose a name that describes a goal or concept they wish to fulfill in life or a concept they wish to personify. These goals can be both good and evil, big and small. The last 3 names in this generator are such names.")

It has already been pointed out a few times, but whatever:
"Tiefling names fall into three broad categories. Tieflings born into another culture typically have names reflective of that culture. Some have names derived from the Infernal language, passed down through generations, that reflect their fiendish heritage. And some younger tieflings, striving to find a place in the world, adopt a name that signifies a virtue or other concept and then try to embody that concept. For some, the chosen name is a noble quest. For others, it’s a grim destiny." - DnD players handbook 5e

So, I believe that usually Tieflings are mistaken for some type of devil/ demon because of the horns and what-not right? Then, depending on their personality, maybe they're aware of this and have some very intimidating grand-sounding name like Master of the field which actually just refers to the fact they have a bunny farm. Idk.
It's indeed a bit of the question what their personality is and their goals and what common tropes you were thinking about.

Maybe a really demonic sounding name with a normal name as a nickname, Nakrael, Rae for short. Idk tho, that might be stupid

This kinda random but what about Erosamn

Female or Male Tiefling?