How interesting and often confusing.
In our family, we have found that there usually are two given names, with the second name being the name by which they commonly were known. For example, Emil Max was known as "Max" and Max Emil was known as "Emil." Same -- often -- for the ladies, except their nicknames usually prevailed. For example, Helene Hedwig was known as "Lena" and Hedwig Martha was known as "Hattie."
It does present challenges for genealogy,
-- Dave