> Stuff like Nyquist criterion just sort of appears out of nowhere as functions.
Black's canonical 1934 paper[1] Stabilized Feedback Amplifiers, which had an outsized influence on EE classical control theory, may have something to do with that:
Results of experiments, however, seemed to indicate something more was involved and these matters were described to Mr. H. Nyquist, who developed a more general criterion for freedom from instability applicable to an amplifier having linear positive constants.
...which directly cites Nyquist's canonical 1932 paper[2] Regeneration Theory.