It’s etymologically indicated that it’s descendent from hot pot, which is also a method of cooking several ingredients in one pot and serving from that pot vs serving individual bowls. It’s called a hot pot because it’s served from a pot that is hot (as it’s the cooking vessel you boiled everything in). Not because the resulting soup is hot. Itself descendent from https://en.m.wikipedia.org/wiki/Pot-au-feu (pot on fire)and similar European dishes