baptist (n.)

"to administer the rite of baptism to," c. 1300, from Old French batisier "be baptized; baptize; give a name to" (11c.), from Latin baptizare, from Greek baptizein "immerse, dip in water," also figuratively, "be over one's head" (in debt, etc.), "to be soaked (in wine);" in Christian use, "baptize." This is from baptein "to dip, steep, dye, color," which is perhaps from PIE root *gwabh- (1) "to dip, sink." Christian baptism originally was a full immersion. Related: Baptized; baptizing.

word-forming element meaning "one who does or makes," also used to indicate adherence to a certain doctrine or custom, from French -iste and directly from Latin -ista (source also of Spanish, Portuguese, Italian -ista), from Greek agent-noun ending -istes, which is from -is-, ending of the stem of verbs in -izein, + agential suffix -tes.

Variant -ister (as in chorister, barrister) is from Old French -istre, on false analogy of ministre. Variant -ista is from Spanish, popularized in American English 1970s by names of Latin-American revolutionary movements.

class of Christians who regard infant baptism as invalid, 1530s, literally "one who baptizes over again," from Modern Latin anabaptista, from Late Latin anabaptismus "second baptism" (used in literal sense from 4c.), from Ecclesiastical Greek anabaptismos, from ana "again, anew" (see ana-) + baptismos "baptism" (see baptism).

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.