PowerShell originally started as a project called “Monad” within Microsoft.
The original Monad Manifesto[PDF] was written by Jeffrey Snover back in August 2002.
BTW, one of the major influences on Monad was a paper by John Ousterhaut:
Scripting: HigherLevel Programming for the 21st Century[PDF]
It’s interesting to read Snover’s original manifesto and see how much of the original vision made it into PowerShell (and how much didn’t).