Here are a couple of blurbs found on the Internet using http://www.google.com
Pass the Buck
(i.e. Shift responsibility onto someone else.) In some card games, a marker called a 'buck' is put in front of the dealer to remind players who is the dealer. When the turn is someone else's, the card is put in front of them-thus, the buck' is passed'.
The original buck' may have been a buckthorn knife. Or, in the Old West, a silver dollar-hence the modern use of the word buck' to denote a dollar.
The expression, The buck stops here' - famously invented by President Harry S Truman and inscribed on a plaque which he kept on his desk -follows on from all this. Truman was a keen poker-player.
Source "Dictionary of Word and Phrase Origins", Nigel Rees
"Passing the buck" comes from the game of poker, where the "buck" is an object placed on the table in front of each player as he or she takes a turn as dealer. The exact origin of the term "buck" for this object is not certain, but it is said that the bucks used in the 19th century poker games were often pieces of buckshot or, alternatively, pocket knives with handles made of buckhorn. When the responsibility for dealing shifted to the next player, the "buck" was passed to that person. "Pass the buck" first appeared in poker jargon around 1865, and was being used in the figurative "talk to my boss" sense by 1900.
~"The Word Detective" Copyright © 2001 by Evan Morris