Because they resemble the identification tags found on dog collars, those worn by military personnel have also come to be known as dog tags. Now popular among civilians as fashion accessories, the tags are officially intended to aid in identifying those killed or wounded in battle. Before dog tags were invented, soldiers were known to scratch their names on the backs of their belt buckles or pin notes with identifying information to their clothing. Why are dog tags usually issued in sets of two? Discuss
Source: The Free Dictionary