This is another of those irrepressibly energetic words that came out of the US in the first half of the nineteenth century. It means uncontrollably exuberant or boisterous.
It’s first recorded in a newspaper report in Boston in 1830:
If they are ‘rumbunctious’ at the prospect, they will be ‘riprorious’ when they get a taste.
The Boston Transcript, 1 Sept. 1830. Riproarious was another bright-eyed and bushy-tailed coinage, also first recorded that year with roughly the same meaning, though the Boston newspaper clearly believed that to be riproarious was to be even more extravagantly uninhibited.
Cautious dictionaries say “of unknown origin”, an open invitation to strange and inventive suggestions. One such holds that it is a compound of ram (to butt or strike) with bust (to thrash or beat), with the implication that rambunctious individuals went around ramming and busting people. Please don’t pass this on.
The Oxford English Dictionary argues that it’s a variant of the earlier rumbustious, recorded from about 1777, that meant boisterous, turbulent or unruly. This had probably been modified in the turbulent and anarchic language of the new frontier through the influence of a number of nouns and adjectives containing –unct–, such as unctuous, compunction, punctilious and perfunctory. The entry points out that rambunctious has also appeared as rumbumptious and rambumptious, suggesting the influence of bumptious.
Rambunctious has been one of the great survivors of the days of American linguistic invention and is still around. It has even crossed the Atlantic to become a British word:
So the days of rambunctious rentiers building big portfolios of properties quickly on the never-never are probably behind us. The property business will be duller without this motley crew, whose members ranged from ex-teachers to fast-talking geezers with diamond ear-studs.
Financial Times, 19 December 2011.