Usage 1: Despite its questionable pedigree (it is of unknown parentage), today's word has produced progeny of its own: a noun (rambunctiousness) and adverb (rambunctiously). I have a strong inclination to allow "rambunction" as a reasonable back-derivation referring to the quality of a rambunctious person but the dictionaries do not allow it yet.
Suggested usage: "Rambunctious" is usually associated with kids who are hard to control. Former President Bush once referred to his son, the current president, as "a rambunctious little guy" in his youth. It has been suggested, however, that rhubarb is a rambunctious vegetable for its uncontrollable power to pucker lips. I suppose the same could be said of a tart apple.
Etymology: A variation of "robust" in the 16th century was "robustious," described by Samuel Johnson in 1755 as "low language." By that time its meaning had changed from that of "robust" to "boisterous, turbulent." A new form, "rumbustious," appeared in print in 1778, along with a mate, "rumbustical," no doubt reflecting the known effect of rum on human behavior. The shift "rum" to "ram" was probably folk etymology, by association with a known rambunctious animal, the ram. Finally, the [n] may be explained by "perserveration," the tendency of sounds already spoken to repeat themselves, e.g. speech errors like "the sheriff shaw" for "the sheriff saw." All of this is purely speculative, of course. (We direct our gratitude today to Dr. Glen Block, Music Director of the Youth Symphony of Kansas City, for bringing the music of "rambunctious" to our ears.)