The Whisky Mac (short for Whisky MacDonald) is apocryphally attributed to various military members of the MacDonald family assigned to posts in India, or Ceylon, or China. There’s no real documented history of the drink, but the stories all lend themselves perfectly to the lightly-smoky, barely-spiced Victorian flavors of scotch and ginger wine.
The scotch that you use should be blended, and mild; ginger wine is the least-spicy ginger-based ingredient, and a big boggy whisky will overwhelm its complex flavors.