The name D’regs is not only a pun on ‘dregs’, but also refers to the Tuaregs, a nomadic Berber tribe in North Africa. The Tuaregs are also the desert marauders who attack Fort Zinderneuf in the movie Beau Geste (based on the book by P. C. Wren).
The name ‘Hersheba’ (a pun on ‘Hershey Bar’ / ‘Beersheba’) is something that Terry came up with in 1992 on a.f.p., when he was more or less thinking out loud about the many people who didn’t get the Djelibeybi reference (the name Djelibeybi puns on the sweets called Jelly Babies):
“[...] say Djelibeybi OUT LOUD — I must have had twenty letters (and one or two emails) from people who didn’t twig until the third time round... oh god... do they have them in the US? Should it have been called Emmenemms, or Hersheba... hmm, Hersheba... could USE that, yes, little country near Ephebe...”