Type of fine, rich-quality English cloth, much valued on the continent; famously made in Stamford in Lincolnshire from the 12c. This cloth was not necessarily scarlet in colour: the term indicated its type and richness. Only later, by transference, did scarlet come to signify the colour. The dye was derived from dried insects (Kermes ilicis) found in the galls that form on the kermes oak (Quercus coccifera), which grew in Spain and Portugal. It was used in the English wool industry between the 12c and the 15c. Scarletum was one 12c Latin form, exscarletum and ascarletum others. [< OldFr. escarlate < Persian saqirlat = scarlet cloth, a rich cloth < Ar. siqillat = fine cloth] -
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.