"If the player did not wish to deal" from Wiki.

This may not be the last word.   Another site says that certainly the buck could have been the marker used in poker, but it had nothing to do with refusing to deal; it was simply procedure to pass the buck (often a knife with handle made of buck's horn) to the next person to deal. The ( buck's horn) knife signified the responsibility to deal. When that dealer was finished, he "passed the buck" on to the next person.