The origins of the Assassins can be traced back to just before the First Crusade, around 1080. There has been much difficulty finding out much information about the origins of the Assassins because most early sources are either written by enemies of the order or based on legends, or both. Most sources dealing with the order's inner working were destroyed with the capture of Alamut, the Assassins' headquarters, by the Mongols in 1256. However, it is possible to trace the beginnings of the cult back to its first Grandmaster, Hassan-i Sabbah (1050s–1124).
Hassani (pronounced Assane) was the first to start this practice. Assassins were a group of people not just a title. Assassins are sometimes (but not always) paid for their work.
It doesn't have to be a special person, an assassin could kill Joe Shmo for cash. There has to be a reason, usually political or religious or even social.