An internet law similar to Godwin's Law, which originated in a myspace political group when people couldn't stop derailing threads. It postulates: "As an online discussion grows longer, the probability of weight or body image being discussed approaches one."
I was just trying to make a point about the difficulties women would face in the military, and all of a sudden someone starts bitching about how larger women aren't accepted in society. Darby's Law strikes again.
The social law that if you hear a reference to an arcane or forgotten word, idea, or person, you will encounter that word, idea, or person again in the near future.
"Yesterday, I learned the word 'soporific,' and then it was used on the Daily Show tonight! It's Darby's Law!"
"Oh my god. There was a major Darby's Law today. I hadn't heard about Bill Nye the Science Guy in years until we talked about him in English class. Then he was in my science textbook the next period."