This article goes into much more detail about why it became popular in the West to adorn textiles with pseudo-Kufic script during the Renaissance:

http://www.laphamsquarterly.org/fashion/crusader-chic

The short version is that it was fashionable in Fatimid Egypt for the ruler to bestow high quality garments to government officials as a sort of promition. These garments usually had verses from the koran embroidered along the hems. The crusaders brought back many of these garments to Western Europe where they became very popular, and the style was imitated in paintings.