Eugene Byrne is a freelance journalist and author, and a regular contributor to BBC History Magazine. You can read his online blog at http://eugenebyrne.wordpress.com/
A curious thing hangs by the thigh of a man, under its master's cloak. It is stiff and hard and bold, and is pierced in front. When the man pulls up his own robe above his knee, he means to poke with the head of his hanging thing that familiar hole which he has often filled before.
The answer is "a key", although you certainly wouldn't be the first person to think it was about something else altogether.
This is the first recorded instance in history of England's far-famed smutty humour and it's from the tenth century. It comes from the Codex Exoniensis, aka the Exeter Book, a collection of Anglo-Saxon writings which was given to Exeter Cathedral by Leofric, the city's first ever bishop. It was probably written sometime between 960 and 990, and probably by Benedictine monks. Most of the writings in it are poetry, including 91 riddles in verse.
It's sort of gratifying to know that this, the largest collection of Old English literature contains quite a few rude bits. While many of the riddles are religious, a few of them are clear double entendres, such as the one above, or the one about the thing that stands upright, is hairy below, and proud maidens like to grip – otherwise known as an onion!