Cowardice was ignoble fear in the face of danger or pain, and that would lead an individual to become a coward. The opposite of cowardice was courage.
In 2267, before T'Pring decided to choose a challenge with Spock, Doctor Leonard McCoy guessed if the opponent would be T'Pau's bodyguard, and T'Pau said that the bodyguard "acts only if cowardice is seen". (TOS: "Amok Time")