Probably came from an inexperienced photographer asking what to say.
Photographer: "What am I supposed to say?"
Person in picture: "Say cheese" (as in a cheesy joke)
Photographer: "Say 'cheese'!"
A word that I invented back in 1999.
A bitchcock is a whining little rooster
who's in need of decapitation. The farmer kills the rooster. Take that BITCH!!!
Bitchcock: "wah wah wah, *cough*, *clear*, I want things my way"