Question

What is the Necessary and Proper Clause? Why has it been called the Elastic Clause?

Answer 1

The Necessary and Proper Clause is known as the Elastic Clause because it one of the most powerful clauses of the US Constitution, it is located on Clause 18 of Article 1.

Article 1 clauses 1 to 17 enlist all the power of the Congress, but Clause 18 of the same article is an “open” or “elastic” clause. It gives Congress the ability to create structures that organize the government and makes possible for the Government to write new legislation to support those explicit powers that are listed in Clauses 1 to 17.

Answer 2

Hey there!
The Necessary and Proper Clause states that the Congress has the 
power to  make all the laws 'Necessary and Proper'  for carrying the Execution.
It has been called the Elastic Clause because it has been used to stretch the power of Congress.

Hope this helps and have a fantastic day! (: