Many will say that it began with Jacques De Molay"s arrest, along with probably hundreds of other Knights Templars on Friday, October 13, 1307 by Philippe le Bel, King of France. De Molay was later executed after suffering horrendously at the hands of torturers...
There is also something about Jesus' Last supper' because there was 13 of them, 12 deciples and Jesus himself. They say this was what cursed Judas to betray or something like that!!
Further to Redheadisbac and Taliesin: at the last supper there were 13 people present (Jesus + 12 disciples, one of whom was Judas Iscariot) and Jesus had previously said of the 12 "Have not I chosen you twelve and one of you is a devil?" (John 6 v70). The theory therefore is that in a (any?) group of 13 one is 'demon-possessed'.