Maybe "herd" is an actual tool, separate from Hurd? Or "and herd" here is equivalent to "et al?" Impossible to search for though.
In December 1991 the primary architect of the Hurd described the name as a mutually recursive acronym:
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