Originally Posted by Angel of Blood
The Emperor named him Konrad Curze when he arrived on Nostromo.
No, the Emperor called
him that. Now, why he called him that is not clear, but there's two explanations possible here.
a) The Emperor named his sons while they were in test tubes and most of them simply ignored his choices and retained the names they'd been given on their homeworlds (although this is strange, since Perturabo suddenly feels like he knows his name when he's first asked about it and then introduces himself to the people who asked him)
b) The primarch needed to adopt some sort of name to interact with various people on Nostramo during the time that his reputation as the Night Haunter was still being built, and the Emperor just picked it out via prophecy or telepathy.
Now, obviously, I think the second option makes more sense. I doubt even a primarch can kill enough important people to become public enemy number 1 of an entire hivevorld over night. That's an entire planet after all, just moving between kills takes forever. And besides, he did love to space his kills in between, to let the effects sink in, to terrorize the people who would be next in line. During that time, the primarch needed a name, an identity, if only not to draw attention to himself.
The story behind the name would be interesting to hear, though. Was it just two words picked at random? Was it the name of one of his victims or someone he wanted to avenge? Is there any baggage attached to his choice?