It started decades ago in my arcade hall and snes times. you were only allowed to enter 3 letters for your scores.
my name is alex, so i always had to enter "ale" and wasnt happy with it
until my sister came up with the idea to use "lx" due to the phonetic resemblance of the english pronunciation of the letters l and x
that felt a lot cooler than ale
when i joined the sesame street seperatists clan playing call of duty and medal of honor i chose cookiemonster as my puppet. in astrowars it first was ccCookiEee (CookieMonster was too long and Cookie was already in use) and later Qki in rememberance of the old times