The word “post”, with very few changes, refers to the post service in many countries in the world; its creation is very old.
"Post" derives from the Latin word "posita", used in the expression "positae mansiones", which designated the "located stops" (positae= put, placed, situated) that were set all along the Roman roads (viae) every 25 or 30 kilometers to make the change or takeover of the horses or other animals pulling travel or merchandise carriages.
In fact this system by changing horses in order to transmit or report messages was created by the Persian king Darius I, who reigned from year 521 to 486 BC. This monarch decided to build a road called the "royal road" which allowed messages to travel along more than 2,000 km linking the shores of the Aegean Sea with the coasts of the Persian Gulf. On this road mails could travel 160 kilometers a day.
Neither the carriage nor the wheel was invented by the Romans, of course. But the practical Latin people did know how to build a heavy but strong carriage dedicated to the transport of people and goods. On it, it was also placed a canopy to protect passengers from the rain or the sun. These carriages were driven all along the huge and solid network of roads and highways that crossed the Empire and made easy to link every place with the capital or main city, Rome. It is in these "roads" where they built the "positae mansiones". Known is the saying "all roads lead to Rome". Roman roads are one of the strongest and most amazing contributions to the economic, political and social life throughout the Empire. Without them, neither the legions nor the goods could move quickly from one place to another. Many of their outlines still match with the large international traffic arteries. In many cases parts of these roads are even preserved. Many of those "mansiones positae" or posts resulted in many contemporary populations.
Precisely the Spanish language keeps two meanings for the word "post", which are straightly related to its origin: "group of horses which were set on the roads with a distance of two or three leagues, so the horses, mails, etc.., could be renewed" and "house or place where the posts were" according to the Dictionary of the Royal Academy of the Spanish Language.
But it is also interesting that the word to name the mail or post service, I mean, the institution or service in charge of sending letters, packages or other effects between two points, in Spanish it is not only the term or word "post" (post service) but also "correos= mails" (mail service), word of unknown origin which also exists in other Romance languages: in French “courrier”, in Italian “corriere”, in Catalan “correu”. Perhaps it comes from the Provencal word "corrieu", formed from "corir = run" and "lieu = place".
The public transport organization created by the Romans since the middle of the first century BC was a revolutionary innovation. The “Cursus Publicus”, as it was called in the administrative language, was an organization or public service for anyone’s use by paying a reasonable retribution or tax.