Why Fear number 13?

The number 13
It is believed that the fear for the number 13 stems from primitive man being unable to count past 12. Numbers beyond 12 do now have an individual and independent name but are a combination of the first 12 numbers. With 12 being the end of the line, 13 was moving into unknown territory.
In Norse mythology the 13th number led to the death of Baldur, the beloved of the gods. When the 12 gods gathered for a banquet in Valhalla, Loki gatecrashed the party, increasing the number to 13, which led to the death of Baldur. It also happens that in Tarot cards, 13 is called “Death.”