I've never found anything to back this up, but my impression was that both the Python / Numpy and Fortran 90 slicing operations were directly inspired by MATLAB

I've never found anything to back this up, but my impression was that both the Python / Numpy and Fortran 90 slicing operations were directly inspired by MATLAB (although most of the ideas go back to at least Algol 68). It also helps that Fortran compatibility is a must for pretty much anything that expects to use BLAS.