Поищите гуглем "pluck yew" - получите ответы на ваш и все смежные вопросы заодно 8)
Вот характерная цитатка из http://urbanlegends.about.com/library/bl-pluck-yew.htm :
ЦитироватьThe middle-finger gesture, which apparently has had phallic connotations in every culture in which it has been used, is much older. We know it dates back at least to ancient Greece, where it was referenced in "The Clouds," a play written by Aristophanes in 423 B.C. It was also well known to the Romans, who referred to it variously as digitus infamis ("infamous finger") and digitus impudicus ("indecent finger"). In all likelihood its origins were prehistoric.