While the exact origin is unclear, it's believed to have emerged in the late 19th or early 20th century in American vernacular speech. The "dag" part is a shortened form of "darn" (another euphemism for "damn"), and the "nab" part is a slang term for "catch" or "grab."
So, "dag nab it" essentially means "darn it, I'm caught" or "darn it, I'm in trouble."
Here's why it might have become popular:
* Euphemisms: The use of euphemisms like "dag nab it" became popular as people sought to avoid using offensive language in everyday speech.
* Regional Dialect: It's likely that the phrase originated in specific regions of the US where certain slang terms and dialects were common.
* Cultural Influence: The rise of popular culture, particularly in movies and television, may have helped to spread the use of "dag nab it" to wider audiences.
It's worth noting that "dag nab it" is a bit of a dated phrase now and is often used in a humorous or nostalgic way. While still understood, it's not as commonly heard in everyday conversation as it once was.