The number 13 has a bad reputation to begin with - But when it falls on a Friday, it suddenly takes on a dire connotation of giant proportions. The phobia is so real and widespread that people suffering from it even have a name - friggatriskaidekaphobiacs. So how did this date and day of the week acquire such bad reputations? While nobody knows for sure, here are a few theories.

First of all there is the irrational fear of the number 13 - While most people fear just Friday the 13th, some, called Triskaidekaphobiacs are afraid of the number, no matter what it is associated with. According to Donald Dossey, a folklore historian, the fear of the number can be traced all the way back to ancient times, when the Vikings inhabited Scandinavia.

12 gods were having a dinner party at Valhalla, the Viking's mythological heaven. Suddenly, an uninvited guest, the mischievous god Loki walked in and instigated Hoder, the blind god of darkness to shoot Balder, the god of joy and gladness. The unlucky number can also be traced to the Bible - Judas, the apostle who betrayed Jesus, was also the 13th guest!

The Friday part is also rooted in ancient mythology and religion - According to the bible, Jesus was crucified on a Friday though the date is not believed to be the 13th. Other biblical scholars maintain that this was the day when Eve tempted Adam with the forbidden fruit - Again, the date is a little hazy. The one bad event that is believed to have happened on Friday the 13th, was the slaying of Abel by his brother Cain (The sons of Adam and Eve).

So how bad is the fear? Experts estimate that businesses lose between $800-$900mm USD on this day because people don't lead their normal lives! The good news is that this year we will have only one Friday the 13th, a fact that has a lot of people signing in relief. Are you superstitious about this day? If so, be sure to add your comments below.

Resources: National Geographic.com, Vancouversun.com,urbanlegends.about.com