As others have stated, Wit represents the more “traditional” way of Intelligence. This is an MC who prefers to think their way out of a problem or a situation whereas a high Influence MC would talk their way out, and a high Combat might muscle instead.
Since I don’t want to add too many stats, I associate other traits with these three main skills. An MC with high Influence, for example, is more attuned to people’s body language, someone’s emotions and base feelings. They probably have an easier time telling when someone is lying to their face.
And, of course, they’re more naturally charming. Their smile shines brighter, their words sound lovelier and their coin seems shinier than all others.
A high Combat MC is highly perceptive on how someone moves. Their knees, their hips, their shoulders. They’re the first ones to know when someone is about to reach for their weapon. They can tell if a target will turn left or right. They enter a room and are immediately aware of all possible exits - all possible vulnerable spots. And whenever they see the layout of a land, they’re the ones you listen to when setting up camp for the night.
And when they fix you with a hard stare, only the strongest of hearts can hold their gaze.
A high Wit MC is one who has spent time with the written word. They know things. Ranks within the nobility, ranks within the Holy Church. Symbols and details, nuances in names, and the history of places. Latin comes easier to them, and they’re the ones who believe that all problems, no matter how twisted, have a solution.
And when faced with madness, they’re the ones who can find reason in the threads. Bring rationality to the world, make others stop and think and perhaps, consider a new point of view.
With all that said, is the word Wit too confusing? Or vague? Should I call it something else? I don’t like Intelligence, because it’s not as if the other skills lack intelligence. And book-smart just doesn’t ring right to me… 
Also, the little sparrow nickname is adorable… (Does he call all MCs that?)
