To be dispirited. This expression is used by thieves to signify that their companion did not die game, as the kiddy dropped down when he went to be twisted; the young fellow was very low spirited when he walked out to be hanged.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Drop Coves * To DrubNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes