dromedary (n.) Look up dromedary at Dictionary.com
late 13c., from Old French dromedaire, from Late Latin dromedarius "kind of camel," from Latin dromas (genitive dromados), from Greek dromas kamelos "running camel," from dromos "a race course," from dramein "to run," from a PIE root *drem- "to run."

It might be from a PIE root *der- (1) "to run, walk, step" (source also of Sanskrit dramati "runs, goes," Middle High German tremen "to rock, shake, sway"). One-humped Arabian camels were bred and trained for riding. An early variant was drumbledairy (1560s).