No, it's not what you're thinking.
And no, it's not that, either!
When I entered the term in Google Images, I was a little worried about what might come up, but there it was, first thing. (The rest of the page was G-rated, too. I can't vouch for later images. Feel free to go explore on your own.)
I wanted to share with you this simple item that can make your life a little more comfortable. It's simply a cloth bag filled with wheat that you heat in the microwave for a couple of minutes and which then stays warm for a half-hour or more. Maybe you've seen them, or used one to ease a sore neck. They cost about $10 at Walgreen's.
Well, I get cold easily. Especially my hands and feet. Bed Buddy to the rescue! I have one at work (where the thermostat is often set at Glacial) and put it around my neck or use it as a wrist rest. At home, I heat one up before I go to bed and throw it under the covers. Once I climb in, it has warmed the sheets a little, and I wrap it around my feet. Cozy!
And this may make you laugh: I took my old tiny microwave (there's a nice new one that came with the kitchen) and put it in the bedroom closet, so I can heat my buddy without running downstairs. It's like living in a fancy mansion with a phone in the bathroom! (Remember when that seemed like the height of decadent luxury?)
Laugh if you will, but my toes are toasty. If you have cold feet, too, give it a try!