Do you know the origin of it?
Mediaeval criminals were hung along with dogs to humiliate them apparently.
at what point in life something like that happens to people...
I think I've got it then. Substitute sand for dirt, and it's when you die and are buried in the ground?
I guess when people praise you, your face blushes with embarassment
It means to be very pleased with or amused by something, but I wouldn't be surprised to find that the origins lie in the face changing colour :)