http://www.43folders.com/2004/09/03/introducing-the-hipster-pda

The original Hipster PDA post? May have been coined before, but this certainly helped to popularize it.

https://mleddy.blogspot.com/2005/03/writing-and-index-cards.html

Looser tradition here for using index cards for writing. Comment have some interesting potential examples from circa 2005