Did he just gerund??

While enjoying a lovely ride in our car on Sunday, our son requested his magnetic writing tablet. (What are those things called anyway??)

"Write!", he said, indicating he wanted his tablet.
Ok, son, here ya go...
and we handed him his tablet.

A few moments later, Daddy and I were back in our conversation when Island Boy declared, "writing!".

"Did he just gerund?!", Daddy asked.

Yes. Yes, I believe he did.

I'm not sure which should impress me more - I mean, how did my husband find that word floating around in his head?? I admit it's been a while since I've used the word, "gerund", and unless you happen to be an English teacher I'm guessing it's been a while since you have, too. :-)