Both Fridays and the number 13 have both been considered “unlucky” down thru the ages.
The number 13, for example:
The Turks so disliked that number that they practically removed it from their vocabulary (Brewer, 1894).
Many cities do not have a 13th Street or a 13th Avenue.
Many buildings don’t have a 13th floor.
And according to information I had a number of years ago, some airlines refused to have a Flight 13 or even a row of seats with that number.
As for the fear of Friday old wives tales say that you should:
Never change your bed on Friday; it will bring bad dreams.
Never start a trip on Friday or you will have misfortune.
If you cut your nails on Friday, you cut them for sorrow.
Ships that set sail on a Friday will have bad luck
From Jeff Strite’s Sermon: It Was Grace That Taught My Heart To Fear