To ban my children from saying certain words?

[theslownorris]

Such as "Why Mummy?"

I can't remember how many questions a day the average 4-y-o asks, but multiply it by 2 for twins and AAARRRGGGHHH.

Shut up is banned in our house and all swear words, although I have caught myself occasionally saying bugger, oops

Thinking about banning "too bad" which dd2 has recently started saying. She says she heard her sister saying it and on actually listening to our conversations this past week I've discovered that dd1 does say it but I say it most of all.