The word “rein” has been used in literature both in a literal sense—as the strap used to control a horse—and in a more metaphorical way to denote the act of restraining or liberating one’s impulses and emotions. In many classic texts, authors employ “rein” to evoke the imagery of control and freedom simultaneously. For instance, St. Augustine uses the image of a loose rein as a metaphor for yielding to sin [1], while Rousseau speaks of giving “rein to passion” to describe the abandonment of self-control [2]. Epic works like Homer’s Iliad feature the rein as a device linking a warrior’s command over his steeds to his fate in battle [3, 4, 5], and in novels by authors such as Tolstoy and Twain the term underscores both a tactical management of physical movement and a symbolic control over ambition or emotion [6, 7, 8]. Across genres—from historical treatises [9, 10] to modern narratives [11, 12]—“rein” continues to serve as a versatile metaphor that captures humanity’s perennial struggle between restraint and unbridled freedom.