It's very stimulating to see such interest in the name 'Bonnyman'. It is quite an uncommon surname and even in Scotland, where it originated, it is very unusual to meet anyone associated with it. There are not many of us about and those that are seem to be scattered around the world !!!!!!!.
I am aware of a textbook (which I have seen in the 'Edinburgh Bookshop - James Thins' which gives what I would regard as the earliest reference to the name appearing in Scotland. Unfortunately I can't remember the name of the book ! (It's a reference text on Scottish surnames), but next time I am in there I will crib the details and post them to this site.
From what I can remember, however, it does categorically state the name as being of Scottish origin and refers to a couple of persons (one being a stonemason in Dunkeld in the 15/16 century and another who was a member of a yeomanry (a sort of voluntary military organisation slightly later). It also refers to the 'Laird of Bonnymooon, who was a small landowner in Scotland and puts forward the idea that the name 'Bonnyman' may have originated from this beginning. In addition it cites the area of 'Angus' which is an eastern county of Scotland within tayside region as being the originating area for the name.
When I have the exact information I will post it to this site - It probably doesn't help anyone, but it gives a bit more background to the name.