A Nutty Business or Monkey Business? Exploring the Origins of a Curious Idiom

The phrase "monkey business" is commonly used to describe mischievous or deceitful behavior. Its origins are believed to date back to the 19th century. One theory suggests it evolved from the term "monkeyshines," first recorded in 1832, meaning "dishonorable act." Another perspective points to the Bengali word "bãdrami," translating to "mischief" or "monkey-like behavior," which may have been adopted into English during the British colonial era in India. The earliest known use of "monkey business" in print dates to 1835. 
Understanding the etymology of such idioms enriches our appreciation of language and its cultural nuances.
Source: Grammarist, Oxford English Dictionary