The main problem is that Pier Giorgio would never be called only "Pier." So, it's a bit disrespectful to him and to his memory. "Pier" by itself is not a name in Italian. It's a prefix. It is always followed by the second part of the person's name. In fact, when the Vatican writes about Pier Giorgio, they usually spell his name as "Piergiorgio." Calling Pier Giorgio just Pier would be something like calling Pope John Paul II just "Pope John." It just wasn't -- and shouldn't be -- done.
Pier Giorgio did have some nicknames, though. When he was a little boy, he gave himself the nickname, "Dodo." Occasionally, he would use "Giorgio," but this was usually when he was writing in German and signing the name "Georg." When he was older, he became a Third Order Dominican and had a religious name (not really a nickname) which he often used. It was Fra Girolamo. (It has occasionally been reported that Pier Giorgio discerned a religious vocation and joined the Dominican Fathers. This is not true. He was only a lay member of the Dominicans.)
The nickname he probably used most for himself was "Robespierre" -- a name originating from the French Revolution. Although it had sinister connotations, Pier Giorgio used the name lightheartedly among his closest friends and gave them nicknames as well.
Pier Giorgio did have some nicknames, though. When he was a little boy, he gave himself the nickname, "Dodo." Occasionally, he would use "Giorgio," but this was usually when he was writing in German and signing the name "Georg." When he was older, he became a Third Order Dominican and had a religious name (not really a nickname) which he often used. It was Fra Girolamo. (It has occasionally been reported that Pier Giorgio discerned a religious vocation and joined the Dominican Fathers. This is not true. He was only a lay member of the Dominicans.)
The nickname he probably used most for himself was "Robespierre" -- a name originating from the French Revolution. Although it had sinister connotations, Pier Giorgio used the name lightheartedly among his closest friends and gave them nicknames as well.