Abraham Simon Wolf Rosenbach was an American collector, scholar, and dealer in rare books and manuscripts. In London, where he frequently attended the auctions at Sotheby's, he was known as "The Terror of the Auction Room." In Paris, he was called "Le Napoléon des Livres". Many others referred to him as "Dr. R.", a "Robber Baron" and "the Greatest Bookdealer in the World".

Robber baron is a term first applied as social criticism by 19th century muckrakers and others to certain wealthy, powerful, and unethical 19th-century American businessmen. The term appeared in that use as early as the August 1870 issue of The Atlantic Monthly magazine. By the late 19th century, the term was typically applied to businessmen who used exploitative practices to amass their wealth. Those practices included unfettered consumption and destruction of natural resources, influencing high levels of government, wage slavery, squashing competition by acquiring their competitors to create monopolies and/or trusts that control the market, and schemes to sell stock at inflated prices to unsuspecting investors. The term combines the sense of criminal ("robber") and illegitimate aristocracy (“baron”) in a republic.