A Spanish girls' name meaning grace.
The daughter born to the Austrian businessman Emil Jellinek was named Mercedes. The brand name Mercedes-Benz was named after her, after first having had a racing team, a line of engines and a number of cars named after her.
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Sources:
http://www.mercedes.com/e/mbclassic/default.htm
http://www.geocities.com/MotorCity/9471/historylink.html