What kind of information in cryptography is called semantic information?
I'm not an expert but...

Semantic analysis is a concept not from cryptography but more from machine learning. The goal is for an AI to learn semantic information from some base set of inputs. For example we might train an AI to detect whether a arbitrary image contains a dog. 

For the purposes of encryption an AI might learn to recognize an individual from a camera, microphone, and/or other inputs. In this case the "semantic information" would be the individual's characteristics necessary for an AI to identify that person from such external data.