Catching Cooties-- Part 1: A World War I to the Playground Thing

From the May 2019 Smithsonian magazine by Jane C. Hu.

Of all the germs kids are exposed to one playgrounds, there's one they freak out about more than any other:  COOTIES.

The word first appeared in World War I as soldier slang for the painful body lice that infested the trenches.

It went mainstream in 1919 when a Chicago company incorporated the pest into the Cootie Game, in which a player maneuvered colored "cootie" capsules across a painted battlefield into a cage.

The cootie concept has be evolving ever since.
The most familiar incarnation on the playground has a lot to do with what the kids think about the opposite sex.  Every little six-year-old girls knows that boys have cooties and vice versa.

One catches cooties by--eww!--touching.  If a little girl gets touched by a boy who has cooties (and they all do), she now has cooties.  But wait!!!  There's a cure.

I Always Heard It Was the Little Girls Who Had Cooties.   --CootieCoot