A nick name for a curious prying fellow; derived from an old legendary tale, told of a taylor of Coventry, who, when Godiva countess of Chester rode at noon quite naked through that town, in order to procure certain immunities for the inhabitants, (notwithstanding the rest of the people shut up their houses) shly peeped out of his window, for which he was miraculously struck blind. His figure, peeping out of a window, is still kept up in remembrance of the transaction.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Peepers * PeepyNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes