a grip on

*a grip on something

 
1. and *a hold on something Lit. a good grasp on something. (*Typically: get ~ have ~ give someone ~.) Try to get a grip on the ropes and pull yourself up. You should get a hold on the knob and turn it firmly.
2. Fig. a thorough knowledge of some topic. (*Typically: get ~ have ~ give someone ~.) I need to have a grip on the basics of accounting. Try to get a hold on all the facts first.
See also: grip
References in classic literature ?
But here was a man who sincerely did not mind what people thought of him, and so convention had no hold on him; he was like a wrestler whose body is oiled; you could not get a grip on him; it gave him a freedom which was an outrage.