Final answer:
The Swiss Brethren were part of the sixteenth-century Anabaptist movement, known for their practice of adult baptism and called 'Anabaptists' because they performed baptisms on individuals who had been baptized as infants in other Christian dominations.
Step-by-step explanation:
The Swiss Brethren were known for their practice of adult baptism, and because of this, they were referred to as Anabaptists, which means "those who baptize again." This name was derived from their belief that only adults could make a conscious decision to commit to Christianity, and therefore, infant baptisms were invalid in their eyes. They insisted that baptism should be a voluntary act of faith, and therefore, they practiced what they regarded as the true first baptism on those who had previously been baptized as infants in other Christian traditions.
Konrad Grebel, a follower of the Swiss reformer Ulrich Zwingli, led in establishing the Swiss Brethren in 1524. Despite initial similarities, Grebel and other Anabaptists eventually found Zwingli's pace of reform too slow, leading to the creation of their own movement with adult baptism as a central tenant.
The term Anabaptist is historically significant as it highlights the central role of baptism in religious controversies during the Reformation period and represents the Anabaptists' challenge to traditional Christian doctrines.