A recent article in the Telegraph explores the stories behind the etymology of phrases in American and British English. Like old wives' tales, some of the more popular explanations for common English words—like "tip" is money given "to insure promptness"—have gained undue credibility. The article debunks some of these errant pop culture interpretations, and offers some surprising explanations. Did you know that the phrase "to curry favor" originally meant "to stroke a fawn-colored horse"? Neither did I. For that phrase, we have a French medieval poem to thank.
For more lexicology and etymology than you can shake a stick at.