When I moved from the coast to the middle of the country when I was 10, I had to learn to adjust my way of speaking to match the local dialect. Slang that I had previously used frequently served only to confuse and bewilder my classmates, who also referred to soda as 'pop', as if they were all thirsty for a tall, refreshing glass of their dad.
When somebody did something particularly spiteful or mean, I would say, "That's cold blooded," but I always said that particular phrase with an accent that I had picked up from my cousins, who I had learned it from. To my new friends, it sounded as if I was saying "That's cah-blay." To this day, when I try to say the phrase like I used to, I can't really understand how they got cah-blay out of cold-blooded. If anything, it sounded like cole-bluht.
Since my entire fourth grade class consisted of compulsive liars, and since they couldn't understand what I was saying, one of my classmates took it upon himself to not only define it, but to inform the teacher about it as well.
"Paul keeps saying cah-blay," he said, loudly enough so that I could hear him, "and it's Mexican for the F-word."
The teacher knew he was completely full of shit, and made stuff up constantly, and I didn't get in any trouble, even though I kept saying it.