Where did he hear that?

I heard Nick use a new phrase tonight and I'm definitely not happy about it. We were headed out to play in the snow and the dogs wanted to go too but they couldn't so they were barking like crazy. He turned around and yelled at them. "SHUT UP!" Truly, I don't know where he heard that one. When I yell at the dogs, I yell "knock it off" and I've heard him yell that at them as well. Shut up isn't even something that Collin says, I wouldn't tolerate it even if it was. AH HA! I just caught the culprit. Tim just walked it and I was telling him about Nick's new phrase and he said that he tells the dogs to shut up when they bark. We need a new rule in our house. If we want to tell the dogs to be quiet, we have to yell things that don't sound awful coming out of our children's mouths.