Originally Posted by
The Pistol
The more I think about it, the term "brick" for me, more aptly describes the feeling in my legs. It was as if I had two bricks strapped to the bottoms of my feet, sorta like running in roller skates on gravel.
Don't know how accurate this info is, but I've always heard it stands for: Bike + Run = ICK.
But your summation is equally plausible.