Why do people, taking photos, say “Say Cheese!” to their subjects? The odds are fairly good for a “Cheeky” smile if saying the word “Cheese!”. The “Ch” sound causes you to clench your teeth and then the long “ee” parts your lips making that grinning expression.
Even though no one knows the origin it became a popular phrase after the Big Spring Herald, a local Texas newspaper, printed an article about “Say Cheese” in 1943. This is the first known documentation.
Back in the 19th century, smiling was only for children, peasants and drunks, neutral was the dignified look. Back in those days the you had to hold that pose, don’t move at all, for a lengthy period of time while the camera worked it magical picture taking abilities. Thus smiling was pretty hard for lengthy periods.
As cameras got better and photographs became cheaper, now you can snap hundreds and just pick the best one, smiling and “Say Cheese!” became prominent.