Good afternoon Navigator
It's good to hear from you and I trust you are still doing well.
Magworth would be better than I at answering your question, but I understand the name Llarragub was first used by DT for the name of a "sow-faced woman" in one of his short stories. In some of the early editions of UMW the name was changed to Llaregyb (against DT's wishes)
I am so enjoying re-reading the book.
Best wishes to you
Mrs Willy Nilly (Jazzgirl)