Merriam-Webster Collegiate Dictionary - usher

 I. noun  Etymology: Middle English ussher, from Anglo-French ussier, usscher, from Vulgar Latin *ustiarius doorkeeper, from Latin ostium, ustium door, mouth of a river — more at ostium  Date: 13th century  1.  a. an officer or servant who has the care of the door of a court, hall, or chamber  b. an officer who walks before a person of rank  c. one who escorts persons to their seats (as in a theater)  2. archaic an assistant teacher  II. verb  (~ed; ~ing)  Date: 1588  transitive verb  1. to conduct to a place  2. to precede as an ~, forerunner, or harbinger  3. to cause to enter ; introduce a new theory ~ed into the world  intransitive verb to serve as an ~ ~ at a wedding