In 1811 slang, what is a Wood Pecker?

A Wood Pecker is a bystander who bets whilst another plays.

What are the rules for King Arthur?

Per the dictionary: King Arthur is a game used at sea, when near the line, or in a hot latitude. It is performed thus: A man who is to represent king Arthur, ridiculously dressed, having a large wig made out of oakum, or some old swabs, is seated on the side, or over a large vessel of water. Every person in his turn is to be ceremoniously introduced to him, and to pour a bucket of water over him, crying, hail, king Arthur! if during this ceremony the person introduced laughs or smiles (to which his majesty endeavours to excite him, by all sorts of ridiculous gesticulations), he changes place with, and then becomes, king Arthur, till relieved by some brother tar, who has as little command over his muscles as himself.

What is a Welch Ejectment?

 Acording to the 1811 dictionary of the Vulgar Tongue a Welch Ejectment is to unroof the house, a method practised by landlords in Wales to eject a bad tenant.

What is a Sleeping Partner?

A Sleeping Partner is a partner in a trade, or shop, who lends his name and money, for which he receives a share of the profit, without doing any part of the business.

editors note:  In modern times this is called a silent partner.

What is a Rag Fair?

 A Rag Fair is an inspection of the linen and necessaries of a company of soldiers, commonly made by their officers on Mondays or Saturdays.

What is Puffing?

Puffing is bidding at an by secret paid assistants at an auction. 

It is also praising any thing above its merits, from interested motives. “The  art of puffing is at present greatly practised, and essentially necessary in all trades, professions, and callings.”

Also To puff and blow; to be out of breath.

What does a Puff (or Puffer) do?

A Puff or Puffer is one who bids at auctions, not with an intent to buy, but only to raise the price of the lot; for which purpose many are hired by the proprietor of the goods on sale.

What are Priggers?

Priggers in a term for thieves in general. Priggers of prancers: horse stealers. Priggers of cacklers: robbers of hen roosts.

What is a Powder Monkey?

A Powder Monkey is a boy on board a ship of war, whose business is to fetch powder from the magazine.

What is a Nypper?

Per the 1811 Dictionary of the Vulgar Tongue: A Nypper is a cut-purse. So called by one Wotton, who in  the year 1585 kept an academy for the education and perfection of pickpockets and cut-purses. His school was near Billingsgate, London.

As in the dress of ancient times many people wore their purses at their girdles, cutting them was a branch of the light-fingered art, which is now lost, though the name remains.

Maitland, from Stow, gives the following account of this Wotton. ”This man was a gentleman born, and sometime a merchant of good credit, but fallen by time into decay. He kept an alehouse near Smart’s Key, near Billingsgate, afterwards for some misdemeanor put down. He reared up a new trade of life, and in the same house he procured all the cut-purses about the city, to repair to his house; there was a school-house set up to learn young boys to cut purses. Two devices were hung up, one was a pocket, and another was a purse. The pocket had in it certain counters, and was hung about with hawks bells, and over the top did hang a little sacring bell. The purse had silver in it, and he that could take out a counter, without noise of any of the bells, was adjudged a judicial Nypper.

According to their terms of art, a Foyster was a pick-pocket, a Nypper was a pick purse, or cut-purse.