This heart I designed recently is very simple, but I haven’t noticed an identical design anywhere so far. The name on one hand comes from the fact that there is a pocket inside the paper that you can use to place a note or a small gift, and on the other “pocket something” means something small and handy enough to fit into one’s pocket which also makes sense.
[Update]: Michel Grand pointed out a number of very similar models: Heart Card by Jeremy Shafer (1996), by Roberto Gretter (2001), Srdce by Ondrej Cibulka (2013) (click through to the first page after the cover here), Broken Hearts by Emily Monaghan (2015), and Cœur en 6 plis by Stephane Gigandet (2015). There’s also a model called Two-Second Origami Heart based on the same idea. Interestingly, those designs among them whose folding instructions I was able to see, all just fold the sheet through both layers in step two while in my design I use two inside reverse folds which results in a more symmetric model and creates the pocket that gives the model its name, but is slightly more difficult to fold.