I'm not a fan of amnesia in ficoitn, or of the variant that I've used: the Memory That Would Solve the Mystery, If Only it Could Be Brought to Mind. I don't like it because, conveniently, it's Brought to Mind just when the plot demands it be.Nor am I a fan of Repressed Memory as it's been used, with similar convenience, in court cases through recent decades.But in a genre that is, classically, based upon the discovery of its protagonists' true natures, it certainly has its place -- think of A Midsummer Night's Dream. And I'd like to try it again sometime.As for period names for ailments: yes, apoplexy for stroke, toxemia for pre-eclampsia, the influenza of course, and the catarrh as well, dropsy (for something or other), melancholy for depression -- and my beloved crapulousness for hangover.