Snowbird has been in use since the late 1600s, but it has only been applied to humans since the early 1900s. It was first used to describe men who enlisted in the armed forces to get food and clothing during the winter months and then deserted as the warm spring weather approached. Not long after, the term was applied to the northern laborers who would flock down south to work as the cold, harsh winter set in up north. Today, northerners of all kinds, from vacationers to retirees, can be seen migrating as soon as the first frost arrives.