"The last will and testament of William Shakespeare"?

[Nessie]

Hi,
As far as I am concerned, "will" and "testament" has the same meaning, so why they say "The last will and testament of William Shakespeare" here:

http://www.william-shakespeare.info/william-shakespeare-the-will.htm
_________________
... something we never have again, I know... I guess I really really know..

Sorry seems to be the hardest word...

[Niobe]

Geoffrey Chaucer

Canterbury Tales - Prologue

The Canterbury Tales is one of the landmarks of English literature, perhaps the greatest work produced in Middle English and certainly among the most ambitious.
Geoffrey Chaucer - The Canterbury Tales is one of the few works of the English Middle Ages that has had a continuous history of publication. Geoffrey Chaucer wrote The Canterbury Tales, a collection of stories in a frame story, between 1387 and 1400. It is the story of a group of thirty people who travel as pilgrims to
Canterbury (England). The tales, some of which are originals and others not, are contained inside a frame tale and told by a collection of pilgrims on a pilgrimage from Southwark to Canterbury to visit the shrine of Saint Thomas Becket at Canterbury Cathedral.
The canterbury talesare written in Middle English. Although the tales are considered to be his magnum opus, some believe the structure of the tales is indebted to the works of The Decameron, which Chaucer is said to have read on an earlier visit to Italy.

More

[Jamie (K)]

[Molly]

This shows how the two words were once used for different actions in the same context:

A will is the legal instrument that permits a person, the testator, to make decisions on how his estate will be managed and distributed after his death. At Common Law, an instrument disposing of Personal Property was called a "testament," whereas a will disposed of real property. Over time the distinction has disappeared so that a will, sometimes called a "last will and testament," disposes of both real and personal property.

http://legal-dictionary.thefreedictionary.com/will