I’ve always thought of this

PHP Hypertext Protocol

When it bears repeating, let’s make it recursive.

Of course not! It’s a drink!

GNU Hurd.

It’s time [to] explain the meaning of “Hurd”. “Hurd” stands for “Hird of Unix-Replacing Daemons”. And, then, “Hird” stands for “Hurd of Interfaces Representing Depth”. We have here, to my knowledge, the first software to be named by a pair of mutually recursive acronyms.

– Thomas (then Michael) Bushnell