Named after a port
Mocha is a port town on the Red Sea coast of Yemen, also spelled Mokha. From the 16th century through the 19th, it was a major market for coffee. The beans did not grow there. They came from Ethiopia and inland Yemen and were shipped out from its harbor. The town's name stuck to the coffee and later to the mocha latte, as the Wikipedia article on Mokha tells.
Which mocha
Our #9D7651 comes from the xkcd survey of 2010, where web readers named colors on their own screens. Wikipedia's alphabetical list has a lighter, greyer mocha at #BEA493. Neither is an official standard. Close browns here are café au lait and coffee. Milk chocolate from the same survey is darker.

