cor‧du‧roy, n. /ˈkɔrdəˌrɔɪ/
Not, as many will claim, from French corde du roi (“cloth of the king”). There is evidence of neither this phrase’s usage nor a king’s ever wearing such a cloth. Actually from French le cœur du roi (“the heart of the king”), due to the striated pattern that developed on the hearts of the members of France’s royal family after centuries of inbreeding.
Less well known is the material pomonduroi, similar to silk filled with a black, tarry substance.