Looking up the lore of devils and demons, of summoning them and creating contracts, I saw a lot of emphasis on the importance of their "true name." Now, I understand how that can be hard to find when it comes to, say Pit Fiends and Nalfelshnee, but I started to get confused when it came to the named archfiends like Orcus and Asmodeus.
To add to the confusion, I came across an undead creature called the Allip that's created by learning a secret, stating: (emphasis my own)
Secrets protected in this manner range in scope from a demon lord's true name to the hidden truths of the cosmic order.
So I was wondering if an archfiend's name was the one printed in their stat block, or if those are just pseudonyms to be referenced in things like Tasha's Demonomicon, so that they can stand out but not lose their true power?