Found a little more info on the actual reason it is said as it is 'Vinegar Hill'
//Phonetic pronunciation of Irish can result in some apparently odd names.
How for example did Vinegar Hill, famous for an important battle fought there in 1798, get its name?
Its Irish name is Cnoc Fiodh na gCaor, understandably something of a mouthful for a non native.
The first part, Cnoc, means hill, so that much is a translation. The second part, Fiodh na gCaor, would phonetically sound like fee-na-gare, so that’s where the Vinegar bit comes from. The Irish name actually translates as “Hill of the wood of the berries”, a much more palatable title!//
Nice little site here.
http://www.dochara.com/the-irish/place-names/irish-place-names/