The question says it all.
Really: where does the name butterscotch come from and what, besides those candies I love, uses this flavor? 
I don’t believe there is any scotch in butterscotch.
The flavor profile you love comes from sugar (which lends a caramel-esque taste), butter, cream, and usually vanilla.
Butterscotch was originally a sort of confection made by spreading the ingredients (basically butter and sugar) in a pan and baking it. The resulting mass was then scotched, or scored with a knife, so that pieces could be broken off. There is also butterscotch sauce for ice cream.
May I flip the question around? How much butterscotch is there in Scotch?
One of the reasons I love a good Scotch whisky is for the lovely “butterscotch” aftertaste. Where does that taste come from? I kinda doubt that anyone would add sugar, butter, etc. to a fine whisky. Is it just a coincidence that the sugars (and other substances) formed during the production of Scotch whisky taste like confectionary butterscotch?
Scotch is made from roasted barley malts; I think it’s reasonable to assume that this caramelizes a little of the sugar in the malts, which carries through into the whisky. I don’t think it’s a “butterscotch” taste so much as a caramel taste.