This expression became a term of encouragement after the following exchange in a live New York local Fox News broadcast at the end of the weather report.
Ernie: "It takes a tough man to make a tender forecast, Nick."
Nick Gregory: "Well, I guess that's me!"
Ernie: "Keep fucking that chicken."
The first line is a parody of a commercial for Perdue chicken from the 1970's, in which Frank Perdue uttered the tag line, "It takes a tough man to make a tender chicken." "Keep fucking that chicken" was the punchline of a joke of the same time about how Perdue did it.