BBB Etymology - From scratch

From 19th century sporting events, specifically the "scratch" drawn in the ground which served (and often still does) as the starting line of a foot race. A runner "starting from scratch" received no handicap or benefit -- whatever the contestant accomplished was due solely to his or her own efforts. So, too, is a cook baking a cake without the benefit of Betty Crocker or her ilk said to be making it "from scratch."