Hard to say - just because it only appeared in the OED a little later doesn't mean to say that it wasn't around prior to that.

I've always understood it to mean "something done to fund something more interesting and possibly superior but which will take longer to complete" which doesn't entirely disagree with the COD's definition or Quinion's explanation.

I've never considered whether it was an Americanism or not. Given that it appeared to emerge during the mid-19th century, the chances are that while it obviously was coined on one side of the pond or the other, it may have become common on both sides fairly quickly, given the literary interchange between the two countries about that time.

Interesting, though, that Quinion's quote talks about paintings, where I had only ever heard it used in relation to literature.

Well, as they say, you live and you learn!