Although Protestant Christians with Baptist principles existed as early as 1609, the name “Baptists” has been used only since the 1640s. Prior to the 1640s, they were variously called “brethren,” “brethren of the baptized way,” “baptized churches,” or derogatorily as “Anabaptists.” Baptists chose the name Baptists because it characterized their preference for believer’s baptism. The name also derived from the practice of immersing baptismal candidates and was often assigned to Baptists by opponents who ridiculed their practice of immersion. Not until the eighteenth century did Baptists widely use this name to describe themselves. Because believer’s baptism (as opposed to infant baptism) is absolutely central to Baptist convictions, it is easy to understand why Baptists have kept this name for centuries.
— Charles DeWeese