fall off the turnip truck
To be gullible, naïve, or unsophisticated. The subject is often a person from a rural or rustic background. Mary has no idea about how to act in polite society, always behaving as if she just fell off the turnip truck. I may have grown up in a small town, but I didn't just fall off the turnip truck—I actually went to college in New York City. A: "OK, just be sure not to make lewd remarks like that during the dinner party." B: "Hey, I know how to act around decent folk! I didn't just fall off the turnip truck, you know."
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.