and the second cropper is from crop and neck--i am guessing cockney rhyming slang, but for what?!

At the end of the eighteenth century English developed a phrase neck and crop, with the sense of “completely”. This is first recorded in a poem by Lady Carolina Nairne:
The startish beast took fright, and flop
The mad-brain’d rider tumbled, neck and crop!

You will find the full history here:
http://www.quinion.com/words/qa/qa-com2.htm