'Stultus' is a Latin word and it means 'Stupid/Foolish'.
stultus is the pseudonym I regularly use on different platforms. If this is not available on a particular platform, I use slightly altered versions like stultusz ,stultuzz or _stultus.
I started to use this pseudonym in IRC chat-rooms in 2008. Those were the days, my friends. Those were the days. Pseudonyms were a thing in IRC. Also I think it is cool to have one. Thus the name and thus the domain name.