Pugnacity, or a natural disposition to be aggressive or belligerent, isn't considered a flattering quality for a person to have. Then again, if you're a boxer, politician, or lawyer, that feistiness might actually come in handy.
Pugnacity comes from the Latin word pugnare, which means to fight. The word pugnacity almost looks like it has the word "nasty" in it, which is fitting since a pugnacious person is one who can be nasty or belligerent. Another way to remember its meaning is to associate the word "city" tucked inside it, with the nature of cities, where people are known to be unfriendly and kind of aggressive.