To send one to Coventry; a punishment inflicted by officers of the army on such of their brethren as are testy, or have been guilty of improper behaviour, not worthy the cognizance of a court martial. The person sent to Coventry is considered as absent; no one must speak to or answer any question he asks, except relative to duty, under penalty of being also sent to the same place. On a proper submission, the penitent is recalled, and welcomed by the mess, as just returned from a journey to Coventry.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
covent garden nun * coveyNathan Bailey's 1721 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes