Internal ID Names are names given to enemies and characters within the code itself. They aren't normally visible and exist independently of the names actually displayed.
A few observations:Lautrec was probably first going to be imprisoned in the Depths, since there is an ID for "HeldKnight_Lautrec" in the area. Held obviously means imprisoned in this context.Tarkus might've been one of Lautrec's phantoms in the alpha. There is an unused ID for Tarkus in Anor Londo, and it's called "Lautrec_Helper", and what else could a helper be but a phantom, especially when Lautrec has two of them?There might've been some kind of betrayal-themed questline for Domhnall, since his character is called "TrickStar" in the internal ID.Priscilla is called "Heroine", probably since she saved Miyazaki with her feet. Manus can be loaded in Darkroot, further confirming that Darkroot was supposed to be Oolacile.