usher: [14] An usher is etymologically a ‘doorkeeper’. The word comes via Anglo-Norman usser from medieval Latin ūstārius, an alteration of classical Latin ōstārius ‘door-keeper’. This was derived from ōstium ‘door’, which in turn was based on ōs ‘mouth’ (source of English oral). The usher’s job-description gradually broadened out from standing at the door to accompanying visitors inside and showing them to their places, which led in the 16th century to the emergence of the verb usher. => oral
usher (n.)
late 13c., "servant who has charge of doors and admits people to a chamber, hall, etc.," from Anglo-French usser (12c.), Old French ussier, uissier "porter, doorman," from Vulgar Latin *ustiarius "doorkeeper," variant of Latin ostiarius "door-keeper," from ostium "door, entrance," from os "mouth," from PIE *os- "mouth" (see oral). Fem. form usherette is attested from 1913, American English.