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2 days agoI’m not sure this is correct, but I’ve heard that flammable and inflammable being used as synonyms is recent. Originally, inflammable meant able to burst into flames without a significant ignition source. Like a pile of oily rags or something that could catch fire because it was left out in the sun or just got too warm.
Yeah, adding in- as a prefix often does mean that, but it can also mean in, on, or into (among others) as a prefix or just part of the core word. And in this case inflammable comes from adding the suffix -able to inflame, a word that already starts with in- in it’s into meaning. And one definition of inflame is “to burst into flames.”