Union suit

Okay, so you know how sometimes it's really cold outside and you have to wear a lot of layers to stay warm? A union suit is like a really warm piece of clothing that covers your whole body in one layer.

It's like wearing a shirt and pants all at the same time, but it's all connected so you don't have to worry about your shirt coming untucked or your pants falling down.

Union suits have been around for a long time and are usually made out of thick, warm material like wool or cotton. They were often worn by people who worked outside or in cold environments, but now they're also worn as pajamas or for fun costumes.

So basically, a union suit is like a cozy full-body onesie that keeps you warm and comfortable.