According to Jim - Season 1 Episode 11

Cheryl leaves Jim in charge of their kids and some friends who were playing with them during a Bears game. The next day, the mom of one of the friends calls Cheryl to report that her daughter came home repeating a swear word she heard from Jim. Cheryl apologizes for him, and he's insulted that she always automatically takes the other person's side. Cheryl apologizes – then Gracie repeats the bad word. Jim decides to teach her not to repeat it by making her say it nonstop until she can't say it again. It works, but at Ruby's ballet presentation five days later, she slips, falls, and uses the bad word.