Reindeer are called reindeer because they are an essential part of Christmas traditions around the world. In many countries, they have been used as a means of transportation and pulled sleighs for centuries. Reindeer are also a symbol of Christmas, and the term "reindeer" was first used in the late 16th century to refer to a type of deer with antlers. Today, reindeer are a beloved part of the holiday season, and many people look forward to seeing them around Christmas time.