The term ‘mouth’ occupies a surprisingly rich and multi-layered position across the depth-psychology corpus, appearing not as a marginal anatomical detail but as a structurally significant site where the somatic, the psychic, and the cosmological converge. Plato’s Timaeus provides the philosophical ground: the mouth is purposively designed as a dual threshold, the passage through which necessity enters (food) and the best departs (discourse), establishing the mouth as a boundary between body and logos. This teleological reading persists in Cicero’s De Natura Deorum, where the tongue, teeth, and palate are praised as instruments of speech — the mouth as instrument of reason’s outward expression. Ancient Greek epic traditions, as traced by Snell and Caswell, locate the soul’s departure through the mouth as the primary aperture of psychic exit, making it a liminal organ at the boundary of life and death. In developmental and embodied-cognitive perspectives, Gallagher and Winnicott converge on the mouth as the first relational organ — the nexus of hand-mouth coordination, orally targeted reaching, and the first possessions. The I Ching tradition, in multiple translations, treats the mouth (K’ou) as the literal site of words going out and food coming in, encoding a cosmological bidirectionality. Rabelais, as read by Auerbach, mythologizes the mouth as a world entire. Together these positions frame the mouth as threshold, instrument, aperture of soul, and first relational site.