MacDonald, Macdonald, and McDonald are Anglicised forms of the Scottish Gaelic name MacDhòmhnaill. It is a patronym where Mac means "son" and Dhòmhnaill means "of Dòmhnall". The personal name Dòmhnall is composed of the elements domno "world" and val "might", "rule". According to Alex Woolf, the Gaelic personal name is probably a borrowing from the British Dyfnwal.
In the context of Scottish clans, the various forms of the name refer to one of the largest clans, Clan Donald.