why do the words “FLAMMABLE” and “INFLAMMABLE” mean the same thing?

ETA: it has to do with some idiot in the 18th century trying to “improve” the english language, and someone taking them seriously around the 1930s. first there was “inflammable”, but then, in the mid-18th century, someone came up with “flammable”, which meant something very similar, but not exactly the same thing, and it died out, fairly quickly, because people were more sensible back then. but then, about the time of world war 2, someone decided that “inflammable” had the same connotation as “invisible” — i.e. “not” flammable — so they came up with “flammable” to convince stupid people that it really was capable of being set on fire. 😒

hell is other people.