it means 'good' and originated from the 'piccadilly palare', slang used in the gaylondon of the 60s
morrissey has an album called 'bona drag' meaning good clothes. in the song 'piccadilly palare' he says 'so bona to vada' which means 'so good to look at/see'
By Lydia
Bona
In modern roman accent means something good (for feminive names) or hot girl.
Bona is the roman version for the standard italian "buona".