Thanks to Julie (on Facebook) for the suggestion of MOON. I immediately think of all the books I'm reading with Little Fingers right now.
Goes great with my next books I'm thinking about after Brown Bear Brown Bear - some of Sandra Boynton's book - The Good Night Book and others!
So the sign MOON - Julie's right - it's in So Many books! So here you go! The sign MOON!
Of course, there's variation - here's two of them (mine is a modified C handshape starting at the forehead and going up diagonally while the other is just a simple whole C handshape doing the same movement).