The term means "calm down" and "back-off," as they relate to being callous about your indiscretions. This may go hand in hand with not considering the ramifications their reveal would have on your life, career, family, and image.
Etymology: Tiger Woods redefined the term when his sexcapades became public in December 2009.
Married Woman #1: I've been chatting with all of these random college girls about hooking up. I think I can convince at least a few to play with me.
Woman #2: Easy, Tiger. I don't think you should be:
1: doing anything to risk your marriage and half of your stuff.
2: telling me, or anybody else about the stupid shit that you do.
3. seeking out fuck-buddies from a pool of those most likely to tell and ruin your life.