” that these words are defined by their anecdotal occasional usage”
They absolutely are. When we randomly through yiddish words into English, it’s a form of slang, so it’s pretty subject to arbitrary colloquial trends. The best example of this is a certain yiddish word that has become so accepted by goyim that they say it as a child-appropriate insult, because they have no idea of its actual translation (I hope you realize what word I’m talking about; I’m worried they won’t let it through). So, you could either climb up on a soap box and proclaim to the goyim that they’re actually saying a very inappropriate word, or you could chill out and admit that colloquialisms change in rather weird ways sometimes.
“Well, the modern orthodox aren’t doing so.”
I don’t know what you want me to tell you; I’ve heard MO people use it my way, you’ve heard it your way. It might depend on locality. Some very Zionistic MO communities are rather anti-yiddish and wish to dissociate with the language and any community that uses it. Of course it’s all anecdotal, it always is with slang. My evidence is anecdotal and your’s is too. I don’t have any problem with you using it your way. It’s you trying to do the censoring here.
I’m not totally tone-deaf to the fact that this isn’t just about disagreeing on the definition of a word. This bothers you because if “frum” excludes MO, that could be seen as an insult/delegitimization of the MO. I concede that you’re right in this sense. But, the MO has consistently used the word “Charedi” in a negative way, they have made it ambiguous as to what one means if he just says the word “Orthodox” alone, and obviously you would be equally offended if we called ourselves something like “real Orthodox.” So, yeah, “you win some you lose some.”