https://www.thehotdog.org/history-of-the-hot-dog/

The story I've heard is that vendor Anton Feuchtwanger (and there's no way to say that without sounding "nasty") offered little sausages at a world's far.. They were popular but dripping with juices and mustard and made quite a mess. Feuchtwanger handed out white cotton gloves to his patrons but the people just walked off and threw the soiled linen in a trash can. Ach du lieber! One morning, his supply of gloves just about gone, Feuchtwanger was about to enter the Fairgrounds and noticed some Kaiser rolls in the window of a bakery. He bought them all, sliced them, and put his greasy sausages within the bread. Hooray! You can say "bread" without being nasty!

My great-great grandfather Henry Oppenheimer invented the sausage casing - err, essentially a discarded intestine from the stockyards - within which the hot dog meats were squashed. You had to "peel" the hot dog before eating it. He made a fortune off the idea until the Chicago Fire burned down his factory. Today hot dogs are pressed and coated with gelatin instead. So you don't have to worry about old intestines, just whatever else is in the meat.