This idiom describes someone who eats greedily, messily, or with poor manners, often consuming large quantities without restraint. It evokes the image of a pig’s voracious and untidy feeding, suggesting a lack of refinement or self-control. The phrase is used in social, familial, or casual contexts, typically with a critical or teasing tone, though it can be affectionate among close relations. It reflects cultural associations of pigs with gluttony and messiness, often carrying a judgmental undertone about dining etiquette or excess.

The phrase likely emerged in 16th-century England, where pigs were symbols of greed and filth in rural life and literature. An early use appears in John Skelton’s 1521 poem *Why Come Ye Not to Court*, describing gluttonous behavior as ‘pig-like.’ The modern form, ‘eat like a pig,’ was common by the 18th century, with Samuel Johnson’s 1755 *Dictionary* noting ‘pig’ as a term for gluttony. It gained traction in the 19th century, as seen in Charles Dickens’ *Oliver Twist* (1838), reflecting Victorian concerns with manners. Its use in American English grew during the 20th century, particularly in domestic settings, where it became a playful or scolding rebuke for messy eating.