Jacques-Alain Miller, Lacan's protégé, traces the idea back to Sigmund Freud's Three Essays on the Theory of Sexuality, out of which Karl Abraham develops the notion of the "part-object", a concept further developed by his student, Melanie Klein, which in turn inspired Donald Winnicott's idea of the "transitional object".
[2]Mary Jacobus writes 'In Lacan's seminars of the late 1950s and early 1960s which seminar exactly?, the evolving concept of the objet (petit) a is viewed in the matheme of phantasy as the object of desire sought in the other...a deliberate departure from British Object Relations psychoanalysis'.
[3] In 1957, in his Seminar Les formations de l'inconscient, Lacan introduces the concept of objet petit a as the (Kleinian) imaginary part-object, an element which is imagined as separable from the rest of the body.
In the Seminars L'angoisse (1962–1963) and The Four Fundamental Concepts of Psychoanalysis (1964), objet petit a is defined as the leftover, the remnant left behind by the introduction of the Symbolic in the Real.
'[7] The third form appears 'at the level of the genital act...[where] Freudian teaching, and the tradition that has maintained it, situates for us the gaping chasm of castration.
'[14] Slavoj Žižek explains this objet petit a in relation to Alfred Hitchcock's MacGuffin: "[The] MacGuffin is objet petit a pure and simple: the lack, the remainder of the Real that sets in motion the symbolic movement of interpretation, a hole at the center of the symbolic order, the mere appearance of some secret to be explained, interpreted, etc."