not know somebody from Adam
not know (one) from Adam
To not know who one is just by looking at them; to have never met one before. Even though Jake had worked at the company for nearly 10 years, the boss still didn't know him from Adam. I don't blame them for not giving me permission right away. They don't know me from Adam.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
not know somebody from ˈAdam(informal) not know who somebody is: This man came into the office and he said that he knew me. I didn’t know him from Adam, which was a bit embarrassing.
Farlex Partner Idioms Dictionary © Farlex 2017