It comes from Alan Moore’s efforts in Watchmen (though Dave Gibbons deserves the credit too). It’s his incredible talent in exploring the logistics of the story-telling in comic books to his advantage. More precisely, it’s the use of texts talking about one subject, and the image showing something different, though both bearing the same core of the message.
The concept is a fascinating literary technique. I’ve found it intellectually engaging to keep perceiving the common message in-between different stories. Sending one message through simultaneous semiotic modalities must be incredibly hard, though.
It requires a very strong sensitivity to analogous situations and metaphors for this to work.
The creation of the symbols also revolves around this idea. For instance, the main idea of the graphic novel itself is to show how the real world would be with super heroes. The blood-stained bottom with the smiley face represents that message with an amazing simplicity and accuracy.
Although I’m not aware of it, surely there’s a official name for this, as I’ve seen it frequently done by other authors. Still it’s been Alan Moore’s use of it that has impressed me the most. I’ve found his attempt especially skillful in the way he merged the Tales of the Black Freighter with his own Watchmen panels.