protocol: [16] Protocol originally denoted an ‘official record of a transaction’. Not until the end of the 19th century, as a reborrowing from French, did it come to be used for ‘rules of etiquette’ (the semantic link is an intermediate sense ‘draft of a treaty or other diplomatic document’, which led to its use in French for the ‘department in charge of diplomatic etiquette’). It goes back via Old French prothocole and medieval Latin prōtocollum to Greek prōtókollon, a compound formed from prótos ‘first’ and kólla ‘glue’ which meant ‘flyleaf glued to the front of a book giving a list of its contents’. => colloid[protocol etymology, protocol origin, 英语词源]