Assumpsit

"...Assumpsit ("he has undertaken," from Latin, assumere) is an action for the recovery of damages caused by the breach or non-performance of a simple contract, either express or implied, and whether made orally or in writing.

Assumpsit was the word always used in pleadings by the plaintiff to set forth the defendant's undertaking or promise, hence the name of the action. Claims in actions of assumpsit were ordinarily divided into (a) common or indebitatus assumpsit[1], brought usually on an implied promise, and (b) special assumpsit, founded on an express promise.[2]
The Common Law Procedure Act 1852 abolished the common law forms of action in England and Wales.

Assumpsit as a form of action became obsolete in the United Kingdom after the passing of the Judicature Acts of 1873 and 1875.

In the United States, assumpsit, like the other forms of action, became obsolete in the federal courts after the adoption of the Federal Rules of Civil Procedure in 1938. Most if not all states have moved to similar rules, which replace the various forms of action with the civil action. However, many states continue to recognize assumpsit as a common law or statutory cause of action..."