Beer... WHAT?

There I was: teaching in my classroom, going over the phonics of letter M when the word beer was blurted out. 

WHAT?

I didn't think I heard the little boy in the front of the class correctly, so I just kept going.  A moment later, he repeated himself.  I was in such shock I didn't know what to say.

How could a little boy know this word?  I bet he was just waiting for my reaction to this, because not long after the word beer was repeated many times came cocktail and whiskey.

WHAT?

I try not to let it bother me, but why does this kid know these words?  Do his parents drink?  Did he get it off of television?  Why does a ten year old boy know the word BEER in a second language?  The situation isn't the worst it could be: he could know some curse words, but why on earth does he know this word!!!?!