It's an old french saying, in french society yougsters were given a knife around the age of 15, even among the poorest families.
So, even if you were broke and had nothing, you still had a dick and knife.
By derivation, used to describe anybody trying to perform an action empty-handed despite some equipement was required.
_Yo pimp, how are you gonna torque this screw ?
_You just came with your dick and knife right ?