Why do they call them dog tags in the military?

The Origin of Military Dog Tags

The expression dog tags has a surprisingly literal history, though its application shifted from four-legged animals to human soldiers over time. During the 19th century, pet identification tags became common practice, laying the groundwork for the concept of physical metal identification.

When military organizations needed a reliable way to identify personnel on the battlefield, they adopted a similar system. The United States military officially introduced identification tags in 1917, requiring soldiers to wear stamped metal pieces that recorded essential data such as name, serial number, and religious preference.

Because these stamped metal pieces bore a striking resemblance to the tags worn by pet dogs, troops quickly began using the slang term dog tags. While the official military nomenclature referred to them as identification tags or identity discs, the informal moniker stuck permanently.

Over the decades, the design evolved from round aluminum discs to the iconic notched rectangular plates worn on a chain during World War II and the Vietnam War. Today, while the materials and exact data formats have modernized, the name remains a permanent fixture of military culture and modern language.