Or Saccocchia. I got bored yesterday and decided that I needed one. (As if I didn't have other things I should have been doing.) It was a very quick and easy little project sewn on the machine except for the rolled hem on the opening and blanket stitches to reinforce the bottom of the opening.
My inspiration came from these images in Moda a Firenze. (Note that these ladies are not fully dressed and the pocket would be worn under the gown accessible through openings in the outer skirt.)