Etymology
Entered use 1890s, origin unknown.
In 2020 James Lambert reviewed previous theories, and supports derivation from:
* boncer (“large marble”) < bouncer (“something prodigiously large”)
Lambert also notes as not supported by evidence:
* bonanza
* French bon (“good”)
* "more fanciful" suggestions:
** born star
** Japanese 万歳 (banzai, “long live..., huzzah, hurrah”)
** bonnie