In the first volume of Momonga takes the name of his Guild 'Ainz Ooal Gown' for himself in order to spread it through out the land in the hopes of getting the attention of his lost friends.However though, that reason sucks. It makes more sense for Maruyama-Sensei to have a better reason for him taking the name. A reason from the very pit and core of Momonga's character.
If that is the sole reason, then why change the name in the first place. Why not use the screen name 'Momonga' that his friends are already used to. It may had to remember a name you only read on a screen, but Yggdrasil was a game you entered. His friends would have walked with, fought besides, and have livid discusion with someone who, for all intensive purposes, was right there beside them. It would be hard to forget him. Latter on he even uses the short had 'Momon' so it makes a good deal more sense to use that.
Similarly he could have used 'Yggdrasil' or 'Nazarick' or something that only other players could have noticed. True he didn't want to get the attention of other players, just his friends, cause he was afraid that the guild's record of Player Killing might bring in powerfull enemies. All the more reason to use something else.
His justification is also a bit flimsy. If he wanted the name 'Ainz Ooal Gown' to spread out in the New World, than it need only be used outside of Nazarick. However he has the NPCs call him by it inside the great tomb aswell. It could be that at the time he was uncertain that Nazarick was secure against scrying attempts(despite the fact that Nazarick has an unnamed World Item that specifically desgined to protect against scrying) and plugged the hole before anything came out. It still shows a desire to be called such both outside in the New World and inside the place were he is safest.
Perhaps it is to show that he is taking complete and total control of what once a majority vote system. As if to say that there is no authority higher than his, because his is the highest authority(this sounds right, but seems to round about itself). This is probably what the NPCs beleived when this incident happend. To support this, in volume three he demonstates this power by doning his guildmate's arms and armour.
All good reasons, but time for the 'what I think'. What I Think is the reason for Momonga to take on the name is to help him cope with what he has done and must do. A trait he should really use more often in my opinion. Maruyama-Sensei loves to remind use that Satoru Suzuki is just a normal salary man and is woefully unprepared for his newfound postion(despit the fact that by now he should have read plenty of books from the library how to rule).
I used to work a shit job, and did it well for a long time. One day I forget my hat at home, big deal at that place trust me. It wasn't my first hat, my lucky hat, or anything like that. It was just an ordinary hat. That day I found myself horribly innadequate and unable to preform to even half my standards. I realized that to me, the hat was a mask. When I put it on I stopped being me and became something else.
When an actor in ancient greace puts an a mask, they stoped being themselves and became their role. When a preist puts on a cerimonial mask, they stop being human and become the god depicted. When a firefighter puts on their uniform, he stop being scared and is able run into a burning building to save a life he doesn't even know. When a soilder puts the uniform, they become someone able to fight, kill, and die for their country.
When he took the name 'Ainz Ooal Gown' he stoped being 'Satoru Suzuki'(in theory).You can see this in his low's and high's. When at his lowest he says "it's impossible, I'm just a salary man I can't do this'. When he's at his peak, when he stand above all other, he bellows with pride 'I am Ainz Ooal Gown. How can this name ever know defeat'. He can no longer say it's impossible. He can only say 'So I just have to do the Impossible than, Easy for Ainz Ooal Gown'(I would love to read this in the light novels).
Wow. I had to type that three times cause the post kept messing up. For real, from scratch. I tried to save it the second time with Copy & Paste, but you can't copy from this box. This time I got the hard copy made in Notepad and pasted it here. So if this feels like fluffy that should be common sense by this point...well. I apologized the first Two times. Please tell me what you think. Yes it got up this time.