Oh man, that's rough. I did the same thing last week trying to call something "fire" and just got a concerned look about office safety. These words move way too fast now. I swear you learn one and it's already over by lunchtime. At this point I'm just gonna stick with "cool" forever, it's safer. We're both clearly better at our actual jobs than we are at slang.
Look, it's just slang. The client got your point even if the word was new to them. People have been messing up slang forever, it's not a big deal. You don't need to chase every new word to do your job well. The whole thing feels way overblown online, like you failed a test. In real life, everyone just moves on.