Why is it bad luck to move on a friday?

A girl at work has just asked this question, is this an old wives tale or is there historic signifcance, please help

A quick google reveals that it is considered unlucky to move
on a friday, but not why.
Apparently, people avoid moving on friday 13th, but otherwise
friday is the most popular day (presumably because you then
have the weekend to recover).

In general, it seems that everything is unlucky on Friday. This probably goes back to the tradition that Christ was crucified on Friday.