Origin of the Name

Although it has sometimes been said that Reid is the Scottish spelling of the surname and Reed/Read/Reade is the English spelling, it more than likely has to do with the inconsistency of our ancestor's spelling of their surnames until the 19th century.
The surname Reid means a red-haired or ruddy person, and legend has it that the progenitor of the Scottish Reid line is Robert the Red (Riach) of Scotland.
Reid is among the 100 most numerous in Ireland and is one of the top forty in Ulster, where it is most common in counties Antrim, Down, Tyrone and Armagh. In Ireland, the surname can be of Irish, Scottish, and English origin.
In England and Scotland Reid is derived from the word red and denoted a person with red hair or of ruddy complexion, the work red in medieval time being pronounced 'reed'.
In Scotland the Islay surname MacRory, from Gaelic MacRuaraidh, became Reid. Also the Scots Gaelic name Ruadh, meaning red almost always became Reid.
In Ulster, the name O'Maoildeirg (Mulderrig), meaning descendant of the red warrior, became Reid. The County Roscommon name Mulready also became Reid.
Reid is a sept or division of the Scottish Clan Donnachaidh , the clan of Duncan and Macbeth of Shakespearian fame.