I searched this site for Donalbain, and found this: user-submitted, but no guarantees.
Anglicized form of Gaelic
Domnall Bán meaning "
Domnall the Fair", a nickname of
Donald III,
King of Scots, the second known son of
Duncan I. This was the form used by Shakespeare in his tragic play '
Macbeth' (1606) for a character based on the historical figure, who allegorically represents moral order.
This clearly supports what Pie said about the meaning being "white", but since it's also said to be a nickname rather than an actual given name, it presumably isn't a suffix as such either.
And, for what it's worth, in the play Donalbain has about three lines and could, on the evidence, allegorically represent moral order, moral turpitude or carpet cleaner. His brother
Malcolm is a far more rounded character.
This message was edited 11/12/2018, 7:44 AM