Symbol for smiling


I've often seen a symbol that is used in context of smiling or happy
expressions. It is sort of a circle with three lines above it.

Can anyone tell me what it's called and where it comes from?

_Example from_ オトメの帝国

[![enter image description
here](https://i.stack.imgur.com/DDfxj.png)](https://i.stack.imgur.com/DDfxj.png)

Other examples from the same manga:  
[example 1](http://postimg.org/image/nlloozgp7/), [example
2](http://postimg.org/image/er5p26uvl/).

I may be wrong in thinking that it has to do with smiles, but I do think it
has something to do with faces.




Just an impression: If your illustrator/author made-up this symbol, it looks
to me like it expresses surprise as in, "Oh!" in context with the character's
emotions. It may be more an expression of feeling than saying, (or having the
character say) "Oh!" in surprise.

