I wish I could cite to authority, my friend on facebook finds the most amazing pics. But she’s not on tumblr nor has a blog so assume she appreciates her privacy and revel in her creativity and persistence in finding these gems.
much to my surprise shit stands for ship high in transit - a reference to guano shipped in sailing ships and having to be kept above the water line lest the guano caught fire. This is why I married my husband. He read the book.