It's called the tontine, a relatively unknown concept in modern times, although it has from time to time featured in various Hollywood movies (notably the novel and movie The Wrong Box). (moneysense.ca)
«While «all - inclusive» is quite a well - known concept in other popular tourist destinations worldwide, it is a relatively unknown concept in this part of the world and we anticipate that it will be very well received. (breakingtravelnews.com)
That is grace — an almost unknown concept in the Old Testament. (redeeminggod.com)