Do the Fiend nicknames mean anything?

[Reversinator]

From what I can tell, if you equip vessels of a certain type to a Fiend, they become a "Noble" and get a nickname, like "Carnal", "Despotic", or "Indignified". Do these change anything gameplay-wise, or is it just fluff?

[Qvnt]

Fluff. Its loosely meant to be an indicator of that Fiend's power and therefore Ranking among other Daemons. Seems to indicate that they curbstop those who rank below them.

[CLG]

It changes based on what level rank of equipment they wear I think, I never really noticed how any of it worked. I'm not even sure if matching pieces of a set gave any sort of bonus either.

[Mì gói khô]

nobles have different voice lines from legions I think

[FaillenOtaku]

It's based on the equipment names. The terms themselves are other words for sins or sinfulness. swap equipment types around that are named different and it will change.