More like a bear than a squirrel. Jeeringly said to any one moving sluggishly on a business or errand that requires dispatch.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
To Quibble * QuidNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes