in the scotch opening if black develops their knight on move 4, this is called the Schmidt variation, does anyone know who it's actually named after?
Eugen von Schmidt (so 'von Schmidt variation' would have been a better name), who was one of the editors of 'Schachzeitung'. His analysis was published in the January issue of 'Schachzeitung', 1865.
For his original analysis (in German, of course), see https://books.google.se/books?id=y61AAAAAcAAJ&hl=sv&pg=PA2#v=onepage&q&f=false .
(Taken almost straight from Oxford Companion to Chess, which has useful info on a large number of openings, the names and their history, at least up to 1992 or so.)