Complex sentence: Reportedly the gang appropriated their name from the Hollywood film star Errol Flynn because they fashioned themselves as flamboyant gangsters in dress and "jitting", or using hand signs to identify themselves publicly.
Split into simpler sentences: Reportedly the gang appropriated their name from the Hollywood film star Errol Flynn because they fashioned themselves as flamboyant gangsters in dress. Also, they used "jitting", or hand signs to identify themselves publicly.