not know from Adam
not know (one) from Adam
To not know who one is just by looking at them; to have never met someone 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.
not know someone from Adam
Fig. not to know someone by sight at all. I wouldn't recognize John if I saw him up close. I don't know him from Adam. What does she look like? I don't know her from Adam.