A dopesheet, often called an X-sheet or camera instruction sheet, used in animation to break things into components (image and a snippet of sound) - nowadays used in digital animation as a collection of animation frames in more of a block, than say a graph.
My question is about its origin not what it is or does:
The earliest known use of the noun dope sheet is from 1895, in Fores's Sporting Notes & Sketches, but what's the story, the word origin, of it getting called dopesheet?
Nobody knows for sure the origin of dope in the sense of information, but it might derive from horse-racing.
Dope has various meanings: sauces, mixtures, and various preparations of chemicals, which are all related, and which seem to lead to the meaning of illegal drug.
It also has another meaning, of information, as in dope sheet (a sheet of information, especially related to horse racing) and dope book (a book of information, especially related to horse racing), which date to the 1890s. The OED says the source of dope=information is unclear (Oxford English Dictionary, “dope (n.1)”). Green's Dictionary of Slang offers no theory.
One of the earliest uses of dope in this context was in relation to horses, so the OED speculates dope sheet and dope book might relate to horses being doped (drugged). Etymonline offers the same theory:
Sense of "inside information" (1901) may come from knowing before the race which horse had been drugged to influence performance (to dope (v.) in this sense is attested by 1900).
There doesn't seem to be very good evidence for this - would anyone really record on paper which horses had been drugged? - but it's the best theory we have.