Big Ben

It is not known where the common name Big Ben came from.

An excerpt from the article 22 facts about Big Ben

This nickname was first applied to the Great Bell. It may have been named after Sir Benjamin Hall, who oversaw its installation, or after English heavyweight boxing champion Benjamin Caunt. Now the term Big Ben is used to refer to the clock, tower, and bell, although it is not generally accepted to refer to the clock and tower. For traditional English people, Big Ben is primarily a bell.