Here's a comprehensive summary of the Wikipedia article on the name Donald:
Donald is a prominent Scottish masculine given name, originating from the Gaelic Dòmhnall, which stems from the Proto-Celtic *Dumno-ualos, meaning "world-ruler" or "world-wielder." Its distinctive final '-d' partially derives from an English misinterpretation of Gaelic pronunciation. The name has short forms like Don, Donnie, and Donny, and its feminine derivative is Donella, though cognates exist in other Celtic languages such as Irish Dónal. Historically, variations of Donald were borne by numerous influential ancient and medieval Gaelic kings and noblemen, including legendary figures like Dyfnwal Moelmud and Scottish monarchs like Donald II (889–900) and Donald III (1033–1099). Today, the name remains widely used, with many notable individuals bearing the full name or its popular short form, Don, across various professions.