Here's the history of this flourish:
This is the fabled DeCourcey Shuffle - named for the Swiss card magician Howard De Courcey (1914-1990).
The interweave at the end (The Notis Cascade) was a further elaboration developed in the 1950s by Senor Notis - an Argentinian card manipulator.
Ricky Jay performed this move in a cameo appearance on an episode of the X-Files in the 1990s - that's when I decided to learn it.