Yesterday, at a gathering of the local Society of Children's Book Writers and Illustrators (SCBWI), I promised one of my colleagues that I'd post a list of the books I use for slang reference here, since I totally blanked on all but one title there. I also thought it might be useful for any other writers here!

The one I lean on at the moment is
SLANG THROUGHOUT THE AGES, Jonathon Green--not only does it list the areas it covers, so you don't have to know the word before you look it up, but unlike most of the more standard books I have, it goes as far back in time as the 1300s. (Think about it--who did the most medieval records-keeping before the 1600s? Monks. Bad for knowledge of slang.) It is a bit limited in that it only covers certain areas, but I still rely on it heavily.

ROGUES, VAGABONDS & STURDY BEGGARS, Arthur F. Kinney, ed., an edited collection of writtings from the 1550s through the 1600s on the subject, including Harman's (most often cited by Green in SLANG THROUGHOUT THE AGES). Solely Tudor and Elizabethan slang, with a glossary in back.

CASSELL'S DICTIONARY OF SLANG. One of those "know the word before you look it up" books, not going back much later than the 1600s, but more and more complete as you come forward in time, a big and chunky book.

SWEARING: A social History of Foul Language, Oaths and Profanity in English, Geoffrey Hughes. As it says, a social history rather than a dictionary, but if you're willing to read the prose, you can dig out some words.

THE SLANG OF SIN, Tom Dalzell. Not very precise at marking the proper time period (generally 1700s to the modern day) for its terms for any kind of vice, crime, temptation, criminal act, or just plain wickedness human beings in the U.K. and U.S. might get up to. It's still interesting, and in some parts the author does identify what time the word is from.