I guessed "Asp". [Hadn't thought of "Ace"; that really was a better choice.] No, wasn't Asp. OK, how about "Art"? No. I was told I was closer with the first guess -- I only had the third letter wrong.
I'm figuring the deities are sending this to me as a test of some sort. Against all hope, I ventured "Ask". He thought this was very funny.
Giving up on my ability to guess a three-letter word for him starting with AS, he told me it was "Ash". I actually managed to get him off to bed before I went into the bathroom and laughed until I cried.