In Jane Austen's 'Pride and Prejudice' why are some place names called "----shire"?

Shires are counties. Yorkshire is the county which includes the city of York for instance.
https://en.wikipedia.org/wiki/Shire

Longbourn is the village in Herfordshire where the Bennets live. It is close to the larger village of Meryton, which is also in Hertfordshire.

When Elizabeth and her aunt and uncle travel to Derbyshire, they stay in the village of Lambton, a few miles from Darcy's Pemberly, which is also in Derbyshire.
http://www.pemberley.com/janeinfo/ppjalmap.html

Hertfordshire and Derbyshire are real shires in England; Longbourn, Meryton, Pemberly, Lambton, etc. are fictional.

I guess my real question was this, then, why don't they just write the full name? It actually says "------------shire". It sort of appears that it has deleted the first part of the word. Is it an expletive that needed to be deleted at some point in time after her writing the novel?

Ah, yes... There was a convention in those days of fictionalising people and places by that means. 'Mrs B----- came to tea yesterday' is an example (doubly fictional...). Nowadays, truly fictional names are used to avoid libel actions, but in Jane Austen it is more for the effect of making things sound a bit diary entry-ish (and also saving the need of researching an actual place). It is a convention that I always find slightly irritating, preferring the fictionalising used by Trollope and Hardy - Barsetshire by the former, and the conversion of Dorchester into Casterbridge by the latter being examples. No expletives in Jane Austen, but other writers might have 'disguised' real people in their rather racier works by this means. Travel writers quite often did this too - presumably adopting the principle that they might go there again, and a copy of the book might get there first... Most of the literature of that period is now a closed book to modern readers (no apologies...) as the style is somewhat impenetrable (Wuthering Heights being a notable exception), but Jane Austen has that delicate sense of irony that still appeals. Sorry, no sources except for Baloo's very extensive reading of obscure stuff.