1540s, as prothogall "draft of a document," from Middle French prothocole (c.1200, Modern French protocole), from Medieval Latin protocollum "draft," literally "the first sheet of a volume" (on which contents and errata were written), from Greek protokollon "first sheet glued onto a manuscript," from protos "first" (see proto-) + kolla "glue."
Sense developed in Medieval Latin and French from "official account" to "official record of a transaction," to "diplomatic document," and finally, in French, to "formula of diplomatic etiquette." Meaning "diplomatic rules of etiquette" in English first recorded 1896, from French; general sense of "conventional proper conduct" is from 1952. "Protocols of the (Learned) Elders of Zion," Russian anti-Semitic forgery purporting to reveal Jewish plan for world domination, first published in English 1920 under title "The Jewish Peril."
protocol pro·to·col (prō'tə-kôl', -kōl')
The plan for a course of medical treatment or for a scientific experiment.