Question

What is the history of the elders of the church being called "the session"? Where did the word "session" come from?

Answer

There is probably a doctoral thesis somewhere or a dusty scholarly tome that has uncovered the origins of the use of “session” in Presbyterian parlance but I have never run across it.

It is not too difficult to trace the general development of the term. Session is a derivative of the Latin sessio from sedere "to sit.” Thus, a session of any kind refers to a sitting down to deliberate over a matter. It is most prominently associated with the sitting of a court to hear legal cases—the court is in session—but we often hear of sundry deliberative bodies having “business sessions.”

Church courts also have their sessions, and the elders involved are properly said to be "members" of the session called to meet about one thing or another. It might even be better to speak of the elders as members of the sessions (plural).

Over the years the expression was shortened so as simply to be rendered session or the session, meaning that the recognized members of the scheduled deliberative sessions formed a single, rarely altered unit.

In theology we speak of “the session of the Father and the Son.” This refers to Christ’s ascension by which He has sat down at the right hand of the majesty on high (Heb. 1:3). This enthronement or sitting of Christ at the Father’s right hand (see also the Apostles’ Creed) portrays the ongoing government of the universe as undertaken by the Triune God.

The Westminster Larger Catechism teaches:

L.C. 54. How is Christ exalted in his sitting at the right hand of God?

A. Christ is exalted in his sitting at the right hand of God, in that as God-man he is advanced to the highest favor with God the Father, with all fullness of joy, glory, and power over all things in heaven and earth; and doth gather and defend his church, and subdue their enemies; furnisheth his ministers and people with gifts and graces, and maketh intercession for them.

It may well be that early churchmen saw in ecclesiastical government a parallel with heavenly government and began to refer to their earthly “sittings” as the sessions of the elders, bishops or whatever. Since early English clerics used Latin in their writings, the term sessio could easily have been transferred into the English language and anglicized as ecclesiastical matters were dealt with.