Sigmund Freud, an Austrian neurologist and one of the most influential thinkers of the 1900s, spent much of his life devoting himself to psychoanalysis, a technique used to treat psychopathology through dialogue. He devoted himself to studying the human brain, and in the short essay The Uncanny, he focuses his writing on ideas that would generally make many people uncomfortable.
To Freud, being uncanny describes a relationship where one is both familiar and unfamiliar with an object. In order to further define uncanny, he borrows the word "unheimlich", which is German for, rather unsurprisingly, familiar and unfamiliar. Hoffman's short story, "The Sand-Man", is referenced in this essay, and it plays with the idea of fear being related to castration. Freud connects the concept with the idea that men believe the genitals of females are “uncanny” places, being the place that everyone originated, and thus being a familiar and unfamiliar “home” to everyone.
Lastly, Freud believes that the term “uncanny” is viewed differently in literature compared to real life. Using fairy tales as an example, he writes that while Snow White coming back to life was nothing too strange for us, the only time that people view moments in literature as uncanny is when the author sets the story in the real world.