The abundant grazing land around the town, suited to sheep farming and wool production, enabled it to become a centre of many textile trades by the 13th century, especially those related to wool. Coventry's prosperity then rested largely on the dyers who produced "Coventry blue" cloth, which was highly sought after across Europe due to its non-fading qualities, and which is believed to be the origin of the term "true blue", i.e. remaining "fast" or "true". According to John Ray in his book "A Compleat Collection of English Proverbs" (1670):