EVERYDAY, without fail, Gavin asks me this question, "So Mom, what word do you have stuck in your head today?"
Some of my better answers are, "Well...seeing as I just woke up, I haven't even thought of words yet." And, "My mind is blank right now, Honey."
Ask me if I have a song stuck in my head and I can type up a list for you. But I don't go around with individual, random words floating through my brain. Gavin does. He only asks the question to be polite. What he really wants to do is tell me the word he has stuck in his head...because he ALWAYS has one. I can't even remember what this morning's word was. He'll come home from school and have yet another word to share with me that has been plaguing his over-worked brain again all day.
I guess if I was immersed in words as often as he is (non-stop), I'd probably get a few bouncing around in my brain all day too. But my advice is, if he ever asks you this, just say the first word that pops into your head. It works everytime.