TL;DR: rot13 of Marco
Probably one of the most common questions people ask me is, where does "znepb" come from? This article finally answers the age old question!
On my 7th birthday, my dad bought me a Minecraft: Java Edition account. He came up with the name MarcoPolo0306: Marco Polo, presumably from the explorer Marco Polo, and 0306 from my birthday, March 6th. I used this name quite consistently up until 2018-ish, though I did go by Xseira/Xsiera for a while because I thought X was a really cool letter and I thought I should use it. No, I am not Elon Musk, or his kid.
Anyways, znepb is ROT-13 encoding of Marco, which I commonly used instead of MarcoPolo0306 because that name is really long. Why is it encoded? I got bored one day on Discord, so I decided to "corrupt" my profile picture by doing some stupid Paint.NET effects on it. Eventually, I decided "hehe i should corrupt my username too!" and ROT-13 encoded it to znepb. I thought the name was kinda cool, so I kept it. The nice part about having the wacky name is that it is usually available when I sign up for websites.
Another question I get asked is, how do you pronounce it? I pronounce it /zənɛp/ (za-neh-buh). But some people say it /zənɛbbi/ (za-neh-pee-bee), or some people just spell it out. It's really just up to you, I don't care. znepb is an online alias, but if you ever talk to me feel free to call me Marcus, just please don't shorten it to Mark.
That concludes this rather short write-up on my goofy username. Thanks for reading, and I hope this answers your question, if I directed you here.