APL, forth and prolog are routinely rediscovered over and over again. They are like a cat standing in the path of a door : refusing the mainstream and refusing obscurity.

Maybe lisp was in that club too but clojure made it mainstream again, by my horribly inaccurate, unscientific and probably wrong reckoning.

It happens like once a year, it's not that sudden. That said, Learning APL looks like an outstanding resource when other introductions to Dyalog are outdated, incomplete, or just low-quality, so I think it deserves to be highlighted even if everyone's otherwise tired of hearing about APL.

I've been reading hacker news for around two years and it's one of the recurrent topics I think. It comes in waves so we may be in a peak of some sorts, but I think it'll always come and go.

The Array Language podcast which started a couple of months ago and was featured on HN has helped.