The story
From the traditional process of removing the layer, removal by jets of water, although the layer can be and often is removed chemically.
Etymology from Wiktionary, CC BY-SA 4.0.
remjet
Today it means: The anti-halation layer on ECN-2, Kodachrome, and several other types of photographic or motion picture film. It is an opaque black coating on the non-emulsion side of the film that is removed before the development process. Full definition →