How did Rafael Trujillo get his nickname?

Trujillo came into power during the revolution of Santiago in 1930. Trujillo and his followers overthrew the government causing the president, Horacio Vasquez, to resign. Since Trujillo was in the military he had to run the take over out of sight as not to be charged with treason. On May 16, 1930 he was chosen to be the president, and he accepted without opposition.