See studies by G. W. Glick (1967) and W. Pauck (1968).
Adolf, also spelled Adolph and sometimes Latinised to Adolphus, was a popular given name, especially in the German-speaking countries, in Scandinavia, in the Netherlands and to a lesser degree in various Central European countries before the regime of Führer Adolf Hitler- particularly among German-speaking Jews living in these countries and sharing their languages and culture, and who previous to 1933 had no reason to avoid the name. It is now a widely avoided name due to its negative association with Hitler.
However, although "Adolfo" as the Italian version of the name has disappeared in Italy, the Spanish version Adolfo has not become stigmatised in the same way. It is still in common use in Spanish-speaking countries, without the parents bestowing it on their son being suspected of Nazi sympathies. The difference is likely due to neither Spain nor the Latin American countries having been subjected to Nazi German occupation.