A person whose job it is to walk in front of another; especially an usher; also figurative. Now specifically in Roman History: a client who walked in front of his patron to clear the way.
Late 16th century; earliest use found in Stephen Gosson (bap. 1554, d. 1625), anti-theatrical polemicist and Church of England clergyman. From classical Latin anteambulōn-, anteambulō person who walks in front from ante- + ambulāre + -ō.