RALPH: The word post first came into the English language from the latin word postis, a stake or pole. Later, it entered English a second time from the Italian posta, which was a way station for travelers and coaches. 
DAVINA: In English, this second usage had a very specific meaning. It referred to the system of stations equipped with horses and riders used to transmit messages, especially to and from the king, sort of like the pony express in the American Wild West. 
RALPH: This evolved into our modern usage as in “postal service”, or post office. 
DAVINA: The witches refer to themselves as “posters of the the sea and land” because they can travel quickly, like the king’s messengers.