Cootie was originally British naval slang for a head lice. It came into common use by the British military during World War I. The word may have originated from the Malayankutu, meaning dog tick, but kutu is also used in many Pacific Island languages to mean head lice.
Cootie is today American children's slang for "germs", lice or a vague notion of contagious personal contamination.
Cootie is also the name of a table game, the object of which is to be the first player to complete a comic model of an insect from the supplied plastic parts, as determined by the roll of a die. The patent is held by Milton Bradley.
The original cooties were very real and extremely nasty, since the word was first applied to body lice.
There was also the cootie catcher, a folded paper shape that you could use to pretend you had discovered cooties on a schoolmate.
The word sounds Scots, and indeed at one time cootie was a good Scots adjective applied to farmyard fowls with feathered legs (it’s probably from cuit, ankle); a cootie could at one time also be a small wooden dish used in the kitchen for various purposes.
Cooties is a fictional disease and a slang word used primarily by North American children to refer to a highly contagious disease or condition.
Cooties also are a deterent to contact with the opposite sex, therefore a form of repression of child sexuality.
Cooties are also used by alpha children to brand their less popular peers as untouchables to the followers of the alpha children, thus establishing social dominance (See bully).