The Mother of All Swear Words - from Jen Wilkin: 

In order to guard your child from acting on natural curiosity in a potentially harmful way, you must become the fountainhead of “forbidden knowledge”, starting with swear words and progressing to sex. You want to be the go-to when your child has a question. Don’t ask an internet filter service to be your first line of defense – attack the problem at its root by inviting your child into dialogue early and often about their questions concerning the forbidden, the embarrassing, the secret. Invite them to trust you as the most reliable and safe search engine they can consult when their curiosity on any topic is piqued.