I can't create a custom game with my summoner name in it

When you create a custom game, the default name is "summoner name's game". Recently, I could not create a custom game under my summoner name. I am keep getting a message that the game's name contains a bad word. I never had this problem before (since season 5). I am looking at my name what could be wrong? Fist? or ful? Maybe the 12? Then I realized that the middle of the name contains the dreaded 4 letter combination (s+t+f+u).

Really, Riot, really? You must have a heck of a word recognition algorithm:)