The kid who is behind you is just some random homicidal kid who has this weird fetish of smelling backs. He is often seen behing little babies or elderly men and sniffing their backs. If he is smelling your back stay still so he doesnt get mad and chop your penis off.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.