Witches?

M: Mom, do you know why we call people witches?
Me: Why?
M: Because we don't know their names.
Me: (confused) Well, we don't call people witches just because we don't know their names.
M: What do we call them then?
Me: Well, we could just say "the lady in the red shirt."
M: (looking around) What lady in the red shirt?
Me: If there was a lady in a red shirt and you didn't know her name, you could just call her the lady with the red shirt.
M: But I don't call everybody witches, just people I don't know.
Me: We shouldn't call anybody witches, honey.

!?! HUH? !?!