It means, you're to blame!

Evan is in this stage where when he hears words he does not know he asks the meaning. So one day when Bill and I were talking something was said and Bill replied, "my fault." Evan immediately asked, "what does fault mean?" Bill and I just look at each other, how do we explain fault to a 3 year old?! So Bill says, "Evan, I'll get back to you. I have to look it up." Evan very calmly replies, "it means... you're to blame!" We were in shock. Did he really just explain to us what a word meant?? I guess our little smarty pants knows more than we thought!