"Rambunctious" first appeared in print in 1830, at a time when the fast-growing United States was forging its identity and indulging in a fashion for colorful new coinages suggestive of the young nation's optimism and exuberance. "Rip-roaring," "scalawag," "scrumptious," "hornswoggle," and "skedaddle" are other examples of the lively language of that era. Did Americans alter the largely British "rumbustious" because it sounded, well, British? That could be. "Rumbustious," which first appeared in Britain in the late 1700s just after our signing of the Declaration of Independence, was probably based on "robustious," a much older adjective that meant both "robust" and "boisterous."

The above is from the MW Word of the Day [I don't have a link]. Too bad robustious passed away, I write with a little tear in my eye...