Apparently, the zettelkasten concept was derived before Luhmann.
boffosocko.com

Zettelkasten Method State of the Art in 1898

Many people mistakenly credit Niklas Luhmann with the invention of the zettelkasten method, so I&#x2019;ve been delving into historical note taking practices. I&#x2019;ve recently come across a well known and...