The senior and junior optimes are the second and last classes of Cambridge honors conferred on taking a degree. That of wranglers is the first. The last junior optime is called the Wooden Spoon.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Open Arse * OrganNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes