not know someone from Adam

not know someone from Adam idiom
Be unable to recognize someone, as in Although I have worked here for two months, I've never seen the department head; I wouldn't know her from Adam. This term refers to the biblical story about the world's first human being. As at least one writer has pointed out, differentiating someone from Adam makes little sense since he had no name and wore only a fig leaf. [Mid-1800s]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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