Madness Monday - Leo the Liar

It all began with a birth certificate.  My husband's father, Harold Arthur Peterson,  was born Oct 3, 1916 to Edwin Peterson and Mable Gibney, in Chicago, Illinois.  I began trying to trace the family through the census, just like any other genealogist. Going backwards was fine.  I found Mable's family back as far as 1860 and Edwin's Peterson line back to the 1880 census in Illinois, although his name varied from Edwin to Edward. 
 
He was born Oct 23, 1883 in Chicago, Illinois to Caroline Neilson and Leopold Peterson.  Edwin (according to Chicago birth records) was the fourth of four children.  The 1900 census shows Edward Peterson living at home with his parents, Leopold and Caroline, in the Hyde Park area of Chicago.  I know Edward/Edwin married Mable Gibney about 1906/07 and they had a son Raymond, born in Chicago in 1908.  After the 1916 birth record of Harold Arthur, I could find no trace of Edward/Edwin and Mable and their family.  I tried everything I would think of.  What happened to them and where did they go?  Harold had married in Chicago in 1938,and the grandparents, Leopold and Caroline, were still in Chicago in the 1920 census, so I didn't think they had left the area.  After years of searching, on and off, I finally found the family in the 1920 census as Leo Peterson and wife Mabel!  Further research reveals that the name change occurred between Oct 3, 1916 ( the birth of Harold Arthur) and Sept 12, 1917 ( Leo Edwin Peterson registers for the draft).  Leo died in 1927 and his widow Mabel remarried which is why the family does not appear in the 1930 census.
Why did Edwin change his name to Leo?  Was it his middle name?  Was it an attempt to identify with his father Leopold?  These are questions that will probably remain unanswered.