A History of Noms De Plume - An Infographic by Printerinks.com

Pen names are as old as, well, books. For centuries, authors have been hiding behind pseudonyms for a plethora of reasons – sometimes personal, and other times political.
But while those reasons differ between each author, some of the more recurring motives provide an intriguing snapshot of historical attitudes; such as the necessity for female authors to go under a male nom de plume around the 19th and earlier parts of the 20th century, in order to avoid gender-based discrimination.
In any case, pseudonyms are a powerful tool for writers and will continue to be so for as long as there is literature.