Not know somebody from Adam

Not know somebody from Adam - to have never met someone and not know anything about them.

Example - "Why should I lend him money? I don't know him from Adam."

Image - http://www.azquotes.com/picture-quotes/quote-eve-said-to-the-serpent-you-know-i-could-go-for-a-bit-to-eat-but-i-don-t-know-you-from-red-buttons-139-35-51.jpg