Cecil’s 1986 column What’s the origin of the mysterious phrase “etaoin shrdlu”? mentions that “etaoin shrdlu” is the order of letter use frequency, “according to one calculation”. The letters were the first lines of the linotype keyboards (more explanation here at World Wide Words), but obviously the "one calculation came much earlier. When, and by whom?
World Wide Words says the name Etaoin Shrdlu appears in a 1931 story by Thurber. The Brown Corpus of 1971 seems to have the frequency order as etaoin srhldc umfpgw ybvkxj qz (or, etoain srhldc umfpgw ybvkxj qz), and Edgar Allan Poe’s The Gold Bug sets it as eaoidh nrstuy cfglmw bkpqxz (notice where the t is, and apparently nobody used j or v in those days).