This is a long one, oh boy...
My first xbox profile was named Dondon843, because my name has a "don" part in it, but not in the way you think. I guess I just liked the descending set of numbers in 843 so I stuck with it. Then, my accounts email got hacked(?) one day and I had to make a new account, it was no biggie though because all my games got switched over. I wanted to take advantage of the name change I had because of the new account, so I named it something I learned in school recently (I was in elementary school at this time), the word Paradigm. I kept the numbers, and therefore Paradigm843 was born! (to this day I still use this xbox account). I got on discord as soon as I hit the age 13, and after jumping around a bunch of don related usernames (ones I remember - Dontheguy, Dondo) I settled on Paradigm843 since I wanted it to be easy to play with me on xbox. After meeting friends, and time passing by, I liked the abbreviations called me during R6S matches (faster to say "Para flanking to cash" than "Paradigm843 to your right") and I changed my discord username to Para. Then, when my friend changed his 4 letter user by one letter, and so I followed suit. Pera was born!
Any other alteration (peradigm, paradigmu, paradime) are whimsical one time things