Thank you!The PAA Filament razor is a fairly faithful reproduction of a 1930s Fasan razor called the Double Slant. So, the name hearkens back to that Fasan vintage razor.
The Double Slant aspect, AFAIK, relates to the fact that the blade is both slanted at an angle and twisted into a helical (corkscrew) shape. The Fasan twist is more extreme than many of the other slant razor designs out there.