Originally in English in reference to the sects that practiced adult baptism and arose in Germany from 1521. Probably so called because, as a new faith, they baptized converts who already had been baptized (as infants) in the older Catholic or older Protestant churches. Modern branches (notably Mennonites and Amish) baptize only once (adults) and do not actively seek converts. The name also was applied, usually opprobriously, to Baptists, perhaps due to the multiple immersions of their baptisms.
popular name of a German-American Anabaptist sect, 1756, from (Pennsylvania) German Tunker, from tunken, dunken "to dip, soak" (see dunk (v.)). So called because they practice adult baptism by triple immersion. The proper name is Brethren.
member of a German Anabaptist sect, 1560s, from name of Menno Simons (1492-1559), founder of the sect in Friesland and chief exponent of its doctrines (adult baptism, refusal of oaths, civic offices, and support of the state in war), + -ite (1). As an adjective by 1727. Alternative form Mennonist (n.) is attested from 1640s.
late 14c., as a type of diving bird, agent noun from dip (v.). As "a ladle or long-handled utensil for drawing liquid," from 1783, chiefly American English. Also "a Dunker, an Anabaptist" (1610s); "one who dips snuff" (1870). As the popular U.S. name for the asterism known in Britain as The Plough or Charles's Wain, attested by 1833, so called for the arrangement of the stars. Compare Big Dipper.