not a penny more

[rskinner]

where and when did it originate?

[rd14962]

As far as I know, it comes from the Shakespeare play The Merchant of Venice, where a pound of flesh was offered as a wager, when the debt is to be paid, the doner is saved when some smart alec mentions the bet was for a pound of flesh, not blood or hair etc. So the removal of the flesh was impossible. A pound of flesh, nothing more nothing less.

Hope this helps!