Its source is an Old French expression meaning "Swarthy."
It is a surname with a number of sources all of which converged in its present spelling.
Among the English, it was derived from an Old French expression meaning ''Swarthy,'' and was given to dark-complected people. Another source for the English surname was more, a Middle English word meaning ''Bog.'' The form of Moore derived from this source was given to families who lived close to a bog or moor.
The separate Irish, Scots and Welsh forms of Moore probably developed through those three branches of Gaelic from a common Ancient Celtic source -- an expression meaning ''Noble, or great.''