This paper presents a historical study on the origin and genealogy of the term 'id' (das Es). In it the whereabouts of the id are followed from its conception to the introduction into psychoanalytic thinking in 1923 (in The Ego and the Id) and to its gradual disappearance from psychoanalytic literature. The main questions addressed in this paper are: (a) How did das Es, as originally conceived by Groddeck, enter the psychoanalytic discourse? (b) What are the main differences between Groddeck's It and Freud's id? And (c) How does the adoption of das Es fit into Freud's general policy of building psychoanalytic concepts?