"We had a good crop this year."
Translation:Bhí barr maith againn i mbliana.
I'm just wondering what I was doing wrong with "bhí barr maith againn an blian seo" as that's what I would normaly say
That would be my guess. I actually asked this to a speaker from Rus Muc Monday, and he said i mbliana is much more common (and native!) but that an bliain seo does mean the same thing.
A borrowed word or phrase transliterated or translated from one language to another. "Galore," for example, is a calque from Irish (go leor) into English. "Milky Way" is a calque from Latin (via lactea) into English.