This idiom describes someone who eats a large amount of food with great appetite, often voraciously or heartily. It evokes the image of a horse consuming substantial quantities of feed, suggesting robustness, hunger, or indulgence. The phrase is used in dietary, social, or familial contexts, typically with a humorous or affectionate tone, though it can imply excess or gluttony. It reflects cultural associations of horses with strength and large-scale consumption, celebrating or teasing abundant eating habits.

The phrase likely originated in 18th-century England, where horses were vital to agriculture and transport, requiring large amounts of hay and grain. It appeared in print by the 1790s, with a 1796 *Sporting Magazine* article noting a man who ‘eats like a horse.’ The idiom gained popularity in the 19th century, reflecting rural life’s familiarity with equine appetites, as seen in Charles Dickens’ *Nicholas Nickleby* (1839). Its use in American English grew during the 20th century, particularly in domestic settings, where hearty eating was often admired. The phrase’s vivid imagery and contrast with ‘eat like a bird’ ensured its widespread use across English-speaking cultures.