to know someone from a can of paint
- idiom
- Informal
- She wouldn't know him from a can of paint if they passed on the street.
Examples
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I don't know him from a can of paint!
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I don't know her from a can of paint, but she seems nice.
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He claimed he didn't know me from a can of paint when questioned.
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Do you really know her from a can of paint?
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I don't know him from a can of paint, so I can't trust his opinion.
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She definitely doesn't know me from a can of paint, despite what she says.
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He insists he doesn't know her from a can of paint, which is true.
Synonyms
To have no idea who a person is at all
Not to know a person at all
To not understand anything about a subject
Antonyms
How Familiar
Surface Forms
Morphology
know + someone + from + a + can + of + paint
The sense 'to not know someone at all' is not derivable from the literal parts — 'can of paint' is irrelevant to familiarity, so the phrase functions as an idiomatic hyperbole rather than a compositional description. This meaning is unpredictable for a B1 learner who merely knows the constituent words and is therefore not transparent cross-linguistically or by ordinary compositional rules.
Etymology
The saying know someone from a can of paint may come from a simple image: a stranger is as familiar to you as an ordinary can of paint, so you 'do not know them at all'.