The verb
eavesdrop is a back-formation from the noun
eavesdropper ("a person who eavesdrops"), which was formed from the related noun
eavesdrop ("the dripping of water from the
eaves of a house; the ground on which such water falls"). An eavesdropper was someone who would hang from the eave of a building so as to hear what is said within. The
PBS documentaries
Inside the Court of Henry VIII (April 8, 2015) and
Secrets of Henry VIII’s Palace (June 30, 2013) include segments that display and discuss "eavedrops", carved wooden figures
Henry VIII had built into the
eaves (overhanging edges of the beams in the ceiling) of
Hampton Court to discourage unwanted gossip or dissension from the King's wishes and rule, to foment paranoia and fear, ==Techniques==