denim: [17] The name of the fabric from which jeans are made had its origins in a sort of serge produced in the southern French town of Nîmes. The French naturally enough called it serge de Nîmes, but the original meaning of this soon became lost when English borrowed it as serge de Nim, and the last two words came to be run together as denim.
denim (n.)
1690s, from French serge de Nîmes "serge from Nîmes," town in southern France. Application to "coarse cotton cloth" is first recorded 1850 in American English. Denims "pants made of denim" recorded from 1868. The place name is Roman Nemausus, said to be ultimately from Gaulish nemo "sanctuary."