The "F" word

When Cade was learning how to read, he liked to play a little game called guess what word I'm going to say, where he would give us the first letter of the word and we had to guess it. One day we were mattress shopping and he came along to the store. He noticed that the salesman was giving out balloons, and I said "I bet if you're good, he might give you one" and Cade said "If he does, I might say the "F" word". Cautiously and curiously I said "Whats . . . the . . "F" . . word? To which he exclaimed "You KNOW, F-F-F-Fank you!"