<digression> Side note: Why is it that you lot say Barkley when we say Berkley for the same spelling. I noticed it studying Bishop Berkley in Philosophy 101 and have always wondered since then. It must be specific to the name, yes? I mean you don't say Harshey Bar, right? I know there are inconsistancies aplenty in our way of doing business over here but, I sincerely wonder, is there an answer to this? </digression>.
It's because our (British) accents have moved on. Back in the 17th Century, Brits would have pronounced Berkeley and Derby as Americans pronounce them today.
Modern American accents and usage have been much influenced by German, Yiddish and Dutch, of course (<digression> which is why Americans write people, whereas Brits write
to them - cf, German
Ich schreibe ihm vs
Ich schreibe zu ihn - English had lost the dative/accusative distinction even by Tudor times & so for centuries has relied on prepositions to do the work that inflections do in German - English is a
deflected, rather than
inflected language - but C19th German/Jewish immigrants to the US simply transposed
ich schreibe ihm onto 'I write him' rather than translate it into 'I write
to him'</digression>), but in as a general principle, colonial accents are much more conservative than metropolitan ones (forgive the solecism, that's how linguists refer to non-English English accents). Shakespeare rhymed 'wind' as in breeze, with 'wind' as in turn, i.e, with 'wined'. We don't any more, but New Zealanders of my acquaintance continue to do so.
So, why not Harshey? Well, generally, changes in a language's pronunciation come from the top down, via emulation of 'prestige accents'. Philip II of Spain had a lisp, which is why modern Castilian Spanish has too. Louis XiV couldn't roll his 'r's in the front of his mouth, which is why modern French rolls its 'r's at the back of the throat.
The English Lords Berkely and Derby and their chums started affecting a drawl (the so-called Mayfair drawl) back in the days of Beau Brummell and the dandies. So Berkeley & Derby became Bahkley & Dahby. The 'conservative' American accent simply preserves the original pronunciation. As best I know, there was no Lord Hershey, and that's why Hershey never became Harsh.
This 'prestige' accent among the late C18th English aristocracy exaggerated a pre-existing tendency in the English English accent toward becoming more and more non-rhotic ('r' silent after a vowel), whereas American accents tend, along with Scots and Irish accents, to favour the pronunciation of the post-vocalic 'r' (rhotic pronunciation). You say 'carr', I say 'cah'. You say 'Berkshire', I say 'Bahkshire'.
The only time an English English-speaker pronounces 'Berk' to rhyme with 'jerk' is in the context of Cockney rhyming slang: 'Berk' is short for 'Berkshire Hunt'. These days, calling someone a 'Berk' is a rather mild insult (& certainly milder than calling them a 'jerk'), but that's only because neither insulter nor insultee aren't generally aware of how bad the insult actually is.
HTH - Better late than never!
p.s., just noticed DWitt's post on David Hume/Home. The last British Prime Minister to come from the House of Lords was a Scottish peer, the 13th Earl of Home, pronounced 'Hume' (better known to history as Sir Alec Douglas-Home, as he resigned his peerage in order to lead his administration from the House of Commons).
