There are woodcuts dated back to the 16th century in Germany featuring a tall, disfigured man with only white spheres where his eyes should be. They called him "Der Großmann" [Sic], The Tall Man. He was a fairy who lived in the Black Forest. Bad children who crept into the woods at night would be chased by the slender man, and he wouldn't leave them alone until he caught them, or the child told the parents what he or she had done. Even then, there is this chilling account from an old journal, dating around 1702:
(Translated from German, some words may be inaccurate)
"My child, my Lars... He is gone. Taken, from his bed. The only thing that we found was a scrap of black clothing. It feels like cotton, but it is softer...thicker. Lars came into my bedroom yesterday, screaming at the top of his lungs that "The angel is outside!", I asked him what he was talking about, and he told me some nonsense fairy story about Der Großmann. He said he went into the groves by our village and found one of my cows dead, hanging from a tree. I thought nothing of it at first... But now, he is gone. We must find Lars, and my family must leave before we are killed. I am sorry my son... I should have listened. May God forgive me."
There is more evidence of the Slenderman, but this is one of the oldest translatable accounts.