Why was my summoner name reset?

It likely got a fair amount of reports, as the name does have some...negative connotations...

I've personally seen worse.

Open a support ticket. Riot support will tell you exactly what the problem is and should allow you to change your name. Well, at least you get a free name change.

Have you been gone for a long time? Someone could have taken the name.

https://en.m.wikipedia.org/wiki/Lolita is the basis of the word.

Also Japan is having a problem with the culture contributing to actual %%%%philia.

So yea.