This is a very, very common thing amongst Irish people when describing a person, place or thing. Because sometimes we can't articulate how large or small an object is, or the skin tone of an individual or even the heat of a local curry dish - we use this a lot! We basically just say the word twice and the person who gets the info knows exactly what we mean by tone alone.
A girl with a very sexy body but an unattractive face... This phrase is generally uttered by men who examine the posterior of a lady as they drive by, On the approach they say "Oooohhh" and if her face does not match the beauty of her posterior as they pass they will say "Naaaaaa", hence Una.
