My first guess would be that you are misspelling it and you mean Bliadhna mhath ùr, anagramming the first word and mixing up "mh" with "bh" in the second. "Bliadhna mhath ùr" means "Happy New Year."
Roughly 'blee-una va oor'.
That a misspelling for Bliadhna Mhath Ùr!Happy New Year! Pronounced as bleeuna vah oor.
Bliadhna Mhath Ùr! [BLEEana vah oor]
Nollaig Chridheil agus Bliadhna Mhath Ùr
The Scottish Gaelic for "Merry Christmas and happy new year"
In Scottish Gaelic Happy New Year is Bliadhna Mhath ÙrPronounced "bleeana vah oor"
Since you did not specify which Gaelic, here are two answersNollaig Chridheil is ScottishIrish would be Nollaig faoi shéan agus faoi shonas duit!
In Irish Gaelic:Athbhliain faoi shéan is faoi mhaise dhuit (singular)Athbhliain faoi shéan is faoi mhaise dhaoibh (plural)Athbhliain faoi mhaise dhuit (singular) dhaoibh (pl.)Scots Gaelic:Bliadhna Mhath Ùr!
In Irish:Comhgáirdeas bhur gceiliúradh (plural)Comhgáirdeas do cheiliúradh (singular)In Scottish Gaelic: Cuirm Bhliadhnail SonaBe aware that 'Gaelic' is actually two separate languages: Scottish Gaelic (called 'Gaelic' in Scotland) and Irish Gaelic (called 'Irish' in Ireland).
It would be Slàinte mhath! in Scottish Gaelic.
Happy New Year is Bliadhna Mhath Ùr (pron. Blee-an-uh Va Oor) in Scots Gaelic. There doesn't seem to be a set expression for wishing someone a happy Hogmanay, which is New Year's Eve. Hogmanay itself is Oidhche Challainn.