The basic sources of this work are Weekley's "An Etymological Dictionary of Modern English," Klein's "A Comprehensive Etymological Dictionary of the English Language," "Oxford English Dictionary" (second edition), "Barnhart Dictionary of Etymology," Holthauzen's "Etymologisches Wörterbuch der Englischen Sprache," Ayto's "20th Century Words," and Chapman's "Dictionary of American Slang." [Anyone know a better guide?]