A Measuring Rod

From The Living Church-

The English word canon comes from the Greek κανών. The term originally pertained to a measuring rod, but eventually referred to the standards which regulated various trades in the ancient world. After the rise of Christianity, it was also used to describe Christian norms. Many readers will be familiar with the phrase “canon of Scripture,” but canon has also been used in other, no less important ways.

 For example, it can describe normative liturgical practice; it can refer to disciplinary procedures; it can denote decisions reached through mutual counsel. Consequently, canon is a word of notable polysemy; appealing to one set of canonical norms refers one to other sets of canonical norms. Canon law is one of the canons used by the Church for maintaining its common life. The canon of Scripture contains “all things necessary for salvation,” but it does not contain all things necessary for running the Church. This latter task is fulfilled by canon law.

A Historical Sketch
The origins of canon law in the Episcopal Church extend through the Church of England back to the medieval period and thus to the early Church. In 325, the Council of Nicaea passed twenty canons for regulating the life and practice of the Church in the Roman Empire. The Nicene canons, which were prefaced by the first version of the Nicene Creed, regulated a large number of jurisdictional, liturgical, and theological matters. Later councils, both Eastern and Western, continued the practice of passing canons.

More here-

http://www.livingchurch.org/measuring-rod