In Swiss historiography, this relates most notably to the Rütlischwur (Rütli Oath) between the three founding cantons Uri, Schwyz and Unterwalden, which traditionally dates to 1307.
The abstraction to the singular use of Eidgenossenschaft, which implies a stronger sense of community and the perception of a strong common cause, did not occur until some forty years later, after the Battle of Sempach, although it began already in the Pfaffenbrief of 1370, a treaty among some of the then eight members of the Swiss Confederacy.
The communal movement in medieval Europe often led to similar alliances or leagues, called conjurationes in the Latin of the official documents of the time.
An early example is the Lombard League at the time of Frederick I "Barbarossa"; an example from Switzerland would be the "Burgundian Confederacy" of Bern.
In the Holy Roman Empire, emperor Charles IV outlawed any such conjurationes, confederationes, and conspirationes in his Golden Bull of 1356.