Answers (1)
A capit is a head. The adjective form is capital. That especially means the head stone on a column. Slogans were often chiseled into capital stones. It is easiest to chisel straight lines, so an alphabet was devised with letters mostly made of straight lines and they are called capital letters. In hand writing it is easiest to make curved lines that flow together, so another alphabet was designed for that purpose. It was called uncial. That means one twelvth. Nobody knows why it was called that, but that is what it has always been called.
A building or a city used as the headquarters of government is a capitol with an 'O'.