There are many towns in Ireland containing the prefix Bally.
Examples are Ballymena (Co.Antrim) An Báile Meánach, The Middle Town; Ballymoney (Co. Antrim) Báile an Mhonaidh, The Town of the Moor; Ballymote (Co. Sligo) Báile an Mhóta, The Town of the Mound; Ballynahinch (Co. Down) Báile na Hínse, The Town of the Holm; Ballymore (Co. Donegal), The Big Town
bally was/still is a very stoned fellow who can often be found in the bars/clubs/streets/houses of south bournemouth. conversation with bally usually includes the phrase 'im fucked mate'. anyone who encounters bally should befriendly, polite and offer him drug based treats.
To walk off on the people you're with to god knows where during a night out, without telling them, for no particular reason.
Usually when completely hammered.