Where did the term "Cheese" come from with portraits

So i have a question here.  Who came up with saying "Cheese" during portraits?  How far does this go back into history? 

It's just a way to get people to seem to be smiling while the shutter is open.

Earlier in the history of photography, many people had bad teeth, so getting people to smile for photos was generally discouraged.

See en.wikipedia.org/wiki/Say_cheese

When taking somewhat "posed" shots of children, even teens, they usually expect me to tell them to say "Cheese", but I throw them a curve and ask them to say "Froggy". It usually causes a bit of a chuckle, but when they say it I get the result that I want, and the shutter clicks just at the very end of their spoken Froggy word. For my taste, it actually produces a nicer and more natural smile. This works well for single and group shots of kids.

Rather than "posing", or taking "pop" shots, for the more serious portrait photo sessions, I tend to prefer having a friendly conversation with my subjects/models to get them more relaxed, and then catch shots of them during the conversation. It just produces more natural images than "posing" does. It sometimes requires more shots to catch the more interesting positions and facial features, but I have found that the better shots usually come from these conversations. I may start out with a few "poses", but then try to get them more relaxed with conversation, and then work to achieve those more natural looking shots during the conversation, usually giving them slight face and body position directions a few times during this conversation. Casual talk about what interests them like hobbies, favorite foods, boy friends, etc. gets their mind a bit off of this "photography thing" and on to "happy things" in their lives. They relax and the shots look more natural because of it. A camera and bright lights in their face evokes a bit of "uncertainty and slight fear in them" because it is a very un-natural thing in their lives. The conversation gets them to relax and think about other things, and you don't get those rigid muscle looks of fear in their portrait shots. Getting them to imagine themselves as "favorite movie characters" sometimes produces some great shots too.    

Charley

Go in front of your mirror and say "cheese" and see what it does to your lips and such