Back in the early days of the internet, I was on IRC playing trivia. Often people would talk about wag or wagging. I didn't know exactly what it meant but I'm pretty good at inferring from context clues... usually.
They asked a Star Wars question and of course I knew it right away. I realized in the moment I was practically wagging in anticipation of being correct and I announced it as my first wag.
Of course, wag stood for wild ass guess so I had gotten the meaning completely backward. It still haunts me to this day, some 35+ years later, even though no one but me probably knew about my mistake.