A headphone or a sunk?

As you saw on this post, Isabella loves to wear headbands. Especially MY new one that I haven't gotten to wear yet because every time I put it on, Isabella starts saying SUNK, SUNK and wants me to put it on her. I have no idea what that word means or where she got it from but a couple of days ago she asked me to play the piano. So, as usual, I put her high chair by the keyboard so she could "play". She started saying: "SUNK, SUNK". This is what I saw when I got there:

Apparently anything that goes on your head is a SUNK. Is she cute or what??