The idiom refers to the purported historical practice of processing equines, particularly those that are old, injured, or otherwise no longer serviceable, into gelatin-based adhesives. This phrase often conveys the idea that something has reached the end of its useful life or has been discarded after its period of service. For instance, a worn-out piece of equipment might be metaphorically described as being “destined for this process,” implying its impending disposal or repurposing.
Historically, while the rendering of animals for various products, including glue, was indeed a widespread practice, the direct and exclusive targeting of equines for this purpose has been debated. The phrase gained traction and cultural significance as a stark metaphor for obsolescence and the unsentimental treatment of resources, be they animate or inanimate. Its prevalence highlights a societal awareness of resource utilization and the cycle of production and disposal.