I've always assumed the call for Kosher Salt in a recipe was because the author of the recipe was Jewish. Whenever I'd see it, I'd make a quick assumption that it was an American recipe, originally created by someone who ate Kosher.
It turns out Kosher salt is a specific type of salt with coarse grains, and often Kosher salt is not Kosher in the religious sense of the world.
It did originate from the practice of salting and making meat Kosher though.
Yes, it's a quiet news day in my house, but this is the sort of thing I find interesting !