Pinned

I was at dinner last night and my grandson was telling me a story about one of his school friends. He said that the friend was acting badly and that made him pinned. He continued the story and again he said that he was pinned. I said that I did not understand what he meant by saying he was pinned. He jumped off of his chair and came close to whisper in my ear. He said that the real word was pissed, but since his parents said he could not use that word, he is using pinned instead. From now on, when people annoy me, I will say I am pinned off.