Taxes, in feudal times, were a way to redistribute wealth from the poor to the rich. The lords and ladies in their magnificent castles lived off the sweat and blood of the peasants who worked their fields and fought their wars.
Death taxes meant that a peasant who died, represented a loss to the lord. The surviving families had to pay a cow or a pig (heriot) in order to recompense the lord for his loss. (sounds like some things never change)
This is different from an estate tax. Ever since the beginning of our constitutionally designed government, an estate tax has been a way of redistributing wealth from those who have profited the most from our society, to those who are struggling. A constitutionally ordained Robin Hood tax, if you will. The estate tax was a part of our political history from before the creation of our constitution, its most eminent proponent being Thomas Paine who argued persuasively for it in his pamphlet Agrarian Justice.
There are two main camps in the estate tax controversy now. The party opposed comprises heirs to large fortunes which they did not create, and are opposed to sharing.
The party in support comprises many mega wealthy individuals who actually created their own wealth, and understand that they owe a debt to the society that allowed them a chance to succeed.
The really sad thing is to see so many of us peasants supporting the right of the super-rich to keep their unearned money. We are still dying in their wars, working in their factories for less and less pay, cleaning their houses, and trying to survive in a crumbling society that cannot provide our children with a decent education, or adequate nutrition, or basic health care.