The coat that survived the trenches and never stopped looking suspicious.
means A long, belted, water-resistant overcoat, typically double-breasted with shoulder straps and a back yoke, originally designed for military officers.
from The name is literal: this was the coat for the trenches of World War I. British officers needed something waterproof and rugged for the mud and rain of the Western Front, and clothiers like Burberry and Aquascutum (the latter had been making waterproof fabric since the mid-1800s) refined existing rain-coat designs into a military garment. The word 'trench' itself comes through Old French 'trenchier,' to cut — a trench being a ditch cut into the earth. So a trenchcoat is, at root, a 'ditch-coat,' which somehow makes its later career in noir films and spy thrillers feel entirely earned.
burberry trench — iconic coat designed by thomas burberry in 1901, became standard british military outerwear in wwi
aquascutum ulster — competing british trench design from 1853, rival to burberry favored by military officers
columbo's raincoat — 1970s tv detective lieutenant columbo's signature shabby trench worn in the series for 45 episodes