Meaning
Not naive and not easily deceived; used to deflect a suspicious claim, offer, or excuse. It appears almost always in the first person ('I wasn't born yesterday') or as a rhetorical challenge ('Do you think I was born yesterday?'). Conversational and a touch wry, typically first person, signalling polite disbelief. Regional use: General English.
Origin
No first use or coiner is documented. Grammarist, surveying the evidence, calls the expression's exact roots hazy but reports that it was appearing in print by the 1800s and has been current since at least the mid-1800s. The logic requires no elaborate backstory: a newborn knows nothing, so anyone not born yesterday has the experience to smell a trick. American familiarity with the wording owes much to Garson Kanin's Broadway comedy Born Yesterday (1946), about a woman written off as naive who proves sharper than everyone around her; the 1950 film adaptation spread the title and the idiom further. Merriam-Webster now enters 'wasn't born yesterday' as a set phrase for a person unlikely to believe something untrue or trust someone untrustworthy.
Research Sources
References used to check this entry’s meaning, history, or documented forms.
Variants
- I was not born yesterday
- I wasn't born yesterday
- was I born yesterday?
- you think I was born yesterday?
Usage Examples
- The dealer swore the caravan had never been towed in winter, but I wasn't born yesterday.
- She accepted the apology graciously; she wasn't born yesterday, though, and kept copies of every invoice.
- You expect the committee to believe the figures were lost in the post? I wasn't born yesterday.