"Howdy!" is the official greeting of Texas A&M University.  It is a way of ensuring that no one feels like a stranger.  The exact origin of this tradition is not known.  However, "Howdy!" is what sets Aggies apart as the friendliest campus in the world and its students love to extend a warm "Howdy!"  to visitors and friends alike.  "Howdy!" is the preferred method for a speaker to get a large group's attention, as the members of the group are expected to return the "Howdy!" back to the speaker.