Friday the 13th and the Templars

My partner believes that the superstition of Friday the 13th originated with the assassination of the Templars, apparently carried out on Friday the 13th after thirteen letters were sent out ordering the Templars in a certain location be rounded up and were executed in the Town Square. I hadn’t heard that one before and after a quick search it sounds to be something popularised only in the 20th century and even moreso since the DaVinci Code was published. I was happy to believe it was of Norse origin though never looked any further into it until today.

He’s adamant that he’s right and none too happy about my DaVinci Code comment. He claims to have read about it some 20 years ago. There seems to be a lot of guess work around the net, loads of different stories can be found. I know Friday has been lucky and unlucky to some for many centuries though what is currently the most widely accepted academic origin of the Friday the 13th superstition?