If someone is insolent, they are rude in a way that shows they do not respect you. It often describes a look, a tone, or an answer — an insolent stare, an insolent reply — more than a long list of bad deeds. It is a fairly formal, slightly old-fashioned word; teachers, novels, and complaints use it more than teenagers in chat. The Latin story is a little surprising: in- meaning “not” plus a piece meaning “being used to,” from solēre (“to be accustomed”). So it started as “unaccustomed / not the usual,” and then came to mean too bold, too proud. You do not need that history to use the word, but it does explain why it is not connected to insole.