About two weeks ago, Ulysses used the word "boo-boo" for the first time. I've never used it, myself -- Don says he's said it. And it's used in a couple of often-seen TV episodes I can think of (Spongebob Squarepants: No Weenies Allowed; Go, Diego, Go: A Boo-Boo on the Pygmy Marmoset) Ulysses didn't just say it; he used it.
We were sitting together at the dining table. I was reading the Web on my laptop; he was atop my lap. (I suppose that makes him the actual laptopper in this story, but anyway...) I shifted position in such a way that the carving under the table scraped against his knee. He whimpered a little, but I didn't react. I was only partly conscious of it; I was reading. He whimpered a little more loudly. I reached out and patted his knee with my hand, glancing at him briefly before going back to reading. Then he said, in a clear, plaintive little voice, "Boo-boo!" The tone meant, "Hey! Don't you get what's going on here?" That stopped my distracted half-interaction. I stopped reading and leaned to kiss the boo-boo'd knee. Ulysses relaxed, and smiled.
A few mornings later, shortly after we'd gotten up, we were walking together in circles in the kitchen. I stopped walking; U walked into me, making slight contact against the back of my heel with his toe. "Boo-boo!" Don walked in to see me kissing U's foot. "Boo-boo?" he said. "Already?"
Now the slightest touch is call for "boo-boo!" Boo-boos everywhere; lots of kisses. Phantom boo-boos arise spontaneously, even while sitting still. Sometimes they travel from one hand to the other; we see him track them. "Boo-boo," he said, one evening, inspecting his right hand. Then his gaze traveled to his left hand, and it was as if his right was forgotten. "Boo-boo." Some third thing drew his mental focus; the boo-boo, evidently, vanished.
A few nights ago, I gave Ulysses an uninvited kiss on the forehead. He didn't like it. He wiped desperately at his forehead, and cried out a little. His voice started to get panicky. Then, all at once, he stopped. His hand held protectively near the afflicted region of his forehead, he looked at me piteously, and said, in a little voice, "Boo-boo." So I kissed his forehead. And somehow, that made it better.