a bedsheet. Used originally for a two sided sheet in the shape of a bag to insert a thin mattress, you would turn over as a way to change the sleeping surface, instaed of changing the sheet.
It's been a few months now, time to change the fartsack.
a one piece blanket sleeper for toddlers, usually zipped up the front. pantlegs are not open at the ankle, but usually enclosed in white slipper-like "footies". worn in the wintertime to keep smaller kids, who might kick off their covers in the night, warm and snuggly.
mom zipped up little fred into a powder blue, winnie the pooh fartsack.