Percy Boyd Staunton, a character in Robertson Davies' Fifth Business, changes his name from Percy Boyd Staunton to, simply, Boy Staunton. This name change comes as a result of the harassment Percy faced while in the army. Percy was constantly made fun of for the name Percy.
After the army, Percy decides to pursue a career in business. Desiring a new life to accompany his new start, Percy Boyd Staunton decides to drop the Percy and the "d" from his name. As Boy Staunton, he finds great success in the investing business (so much so that he is able to care for himself and for Dunstan Ramsay. Boy's success is so great that he surpasses his own father's wealth and success.
In essence, the reasoning behind Percy's (Boy's) name change lies in his desire to start a fresh new life without ties to his old one.