What does DOG tag stand for in the US military?

Answer 1

military Id tags are worn around the neck with a chain. there are two of them. if a military member is killed one of the tags is removed and forwarded to graves registration for reporting. since the tags 'look' like DOG tags, the slang word DOG-TAGS became part of military slang when referring to ID. tags..................

Alot of people called those among the ranks of the military the military dogs. The name of dog tags may be referring to the military owning them and them being the dogs of the military.