Say what?

I have a private class every Thursday with three friends, Rosa's girl, and two boys, all in second grade. They are slightly crazy, intelligent, and fun to be with when they're motivated...horrible when they're bored. Last week, like after each class, the four of us cleaned up the room. One erased the dry erase board, another put the chairs away, and the last put the game or flashcards in an envelope while I collected the books and the rest of my things.
A few seconds into this activity, I hear one of the boys say clearly, "Hey baby."
Surprised, I turned around and asked, "What did you say?"
"Hey baby," he repeated, and then continuing in Spanish said, "you know, when someone who speaks English has a baby boy or girl, sometimes they say to them, "Hey baby" instead of saying their name.
That made me laugh. Where do they get these ideas?