I don't know if this will help, but I have this impression that when the name first started being used in GW publications, like the BBB, they were the 40k equivalent to Skaven. Do you have that "other xenos" image from the 3rd edition rulebook? It has a picture of pre-Tau Kroot, "Clawed Fiend of the Donorian Sector," Tallerian Dog Soldier (I'm working on a custom list and army of them just like your Hrud project), a Hrud, etc. Also, in the IG Codex there's a note about the 39th Cadian "Xenobane" regiment, page 31, who were involved in the "Chincare Hrud Infestation, M41," which suggests a few things to me. The word infestation is important to me, and I think it also is an indication that the Hrud are obviously worthy adversaries. Best of luck.