sumpter (n.) Look up sumpter at Dictionary.com
c.1300, "driver of a pack horse," from Old French sommetier "pack-horse driver," from Vulgar Latin *sagmatarius "a pack horse driver," from Late Latin sagmat- "a pack, burden," stem of sagma "packsaddle," from Greek sagma, probably related to sattein "to pack, press, stuff." Used from mid-15c. of horses and mules for carrying loads.