The exceptio non adimpleti contractus is a defence that can be raised in the case of a reciprocal contract. In essence, it is a remedy that allows a party to withhold his own performance, accompanied by a right to ward off a claim for such performance until the other party has duly performed his or her obligations under the contract.
Origins in the Roman Law.
The first use of such defence was attested in the historical sources in concern to the Roman Law. There, it was used as an "'exceptio"', i.e. in response to a legal claim from the other party in a contractual obligation.
Requirements for the "exceptio non adimpleti contractus".
Two requirements must be met in order for the "exceptio non adimpleti contractus" to be available. The two performances must be reciprocal to one another; and the other party must be obliged to perform first.
In the Continental Legal Systems.
It is provided in the legislation of all European countries using the Civil Law System, especially those with strong influence from the Napoleonic Code (1805). 
References.
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