Merriam-Webster's Collegiate® Dictionary, 11th Edition
COACH
I. noun
Usage: often attributive
Etymology: Middle English coche, from Middle French, from German Kutsche, from Hungarian kocsi (szekér), literally, wagon from Kocs, Hungary
Date: 1556
1. a large usually closed four-wheeled horse-drawn carriage having doors in the sides and an elevated seat in front for the driver, a railroad passenger car intended primarily for day travel, bus 1a, trailer 3b, a 2-door enclosed automobile, a class of passenger air transportation at a lower fare than first class,
2. \from the concept that the tutor conveys the student through examinations] a private tutor, one who instructs or trains ,
II. verb
Date: 1630
intransitive verb to go in a coach, to instruct, direct, or prompt as a coach, transitive verb to train intensively (as by instruction and demonstration) , to act as coach of , coachable adjective coacher noun