Few laymen know that the expression ‘the pleadings’ in an action denotes the written allegations of fact which each party is required to communicate to his opponent before trial, in order that each may know what contentions he will have to meet, if possible, by evidence, and that an issue, or issues, of fact or of law may emerge. This unexpected meaning comes down in direct descent from the Middle Ages, when opposing counsel strove in Court to extract an issue from the conflicting pleas (placita) submitted by them orally.
Thirteenth century.
During the earlier part of this country proof was formal and the function of the Court was to declare which of the parties must go to proof and how. In certain classes of cases proof by battle was appropriate, in others proof by oath—either the oath of the party, supported by oath-helpers, or the oath of witnesses.