[Twisol]

Yep! I remember the phrase "functional core, imperative shell" being popularized by Gary Bernhardt in ~2012 [0][1]; in his talk Boundaries [0] (around 31:00), he even mentions "hexagonal architecture" by name.

[0]: https://www.destroyallsoftware.com/talks/boundaries

[1]: https://www.destroyallsoftware.com/screencasts/catalog/funct...