Lefferti (sing. lefferto) is a colloquial term referring to mostly younger European "down-timer" men, usually wealthy and otherwise idle younger sons of noblemen, who emulated the Americans' style of dress and personal mannerisms that became so very popular throughout Europe. The term is named after American Harry Lefferts, thanks to his travels and the manners (i.e. brawling and drunkenness) that he displayed during them. He inadvertently helped spread the lefferti culture during his visit to Rome in 1633 while accompanied by Giulio Mazarini. While the lefferti style was just style for some, others also adopted some of the Americans' social and political ideas.
Rome's lefferti were generally opposed to Cardinal Borja's seizure of power, and many took part in the failed attack on the insula Mattei. Many of them were killed, and afterward, Rome's lefferti were either hunted down and killed, or went into hiding.