Literal translation is "I don't know what those boys are on about" or near enough. Loons are boys in a dialect of the North East of Scotland.
Must admit I'm cheating a bit as I don't speak it as I'm really from the cental belt though I can understand most of it though context and a few words I know. But there's a lot of dialect in the Brittish Isles.
Not meaning to highjack but I love the different accents, regional words, accents and slang in Britian. I know more about it in Scotland but the Yorkshire words are great too.
Funny how these things spring up and with some people you can pinpoint where in the country they were brought up. I do have particular favorites: Orkney, the Western Isles, Shetland, the Borders, Fyfe and Dundonian all have particular traits and quirks in their language that I like and can pick out