The surname Reid was originally a nickname and evolved in recognition of the physical or personal attribute of a particular individual. In this regard, the name can be traced to the Old English expression of “read” meaning “red” and it would have been used to identify a person who had red hair and a ruddy complexion. This name first appeared as “Rufus” in Latin written records in the thirteenth century. Here mention is made of a person named Ade Ruffus who witnessed a record of the transfer of lands in 1204.

The Reids were a branch of the noble Robertson Clan, who took their name from their chief, Robert, in celebration of the capture of the murderers of King James I in 1437. They then controlled territories in Kyle, where William Rede, son of John Reede, was promised the lands and effects of the territory of Bairskemyn in 1375. Later, another William Rede purchased the lands of Wester Pitfoddels from his cousin Alexander de Moravia and established his family there in 1389. However, it should be noted that in certain cases, this name may have been derived from the Gaelic term “ruadh” which also means “red”. Therefore, some bearers of this name in Scotland may trace their ancestry to one Alaister Ruadh of Strathardie, who lived in the fifteenth century. General John Reid, composer of the air “The Garb of Old Gaul” and founder of the Chair of Music at Edinburgh University, was one of those and he was the first member of his family to add an “i” to his surname, Red, in the late seventeenth century.

There are several independent Scottish, English, and Irish origins of the Reid name, and we cannot be certain of the exact origin.

In Scotland, the Islay name MacRory, Mac Ruaraidh in Gaelic, became Reid, and the name Ruadh, meaning red, also became Reid. The name MacInroy, or Mac Iain Ruaidh in Gaelic - "son of Red John" - a sept of Clan Donnachie, was changed to both Reid and Roy. Tradition says that the progenitor of the Reid sept of Clan Robertson is 'Robert the Red' of Scotland.

In both England and Scotland the names Reid, Reed, and Read can derive from the word for "red" implying that the progenitor of the family name was someone with red hair or a ruddy complexion. In Old English, 'ried' refered to a residence in a clearing. English roots of the name can also be connected to the towns of Read in Lancashire, Rede in Suffolk, or Reed in Hertfordshire.

Reid is among the 100 most common names in Ireland, and among the 40 most common in Ulster. It is particularly common in the counties of Antrim, Armagh, Down, and Tyron. In Ulster, the name Ó Maoildeirg or Mulderrig, meaning "descendant of the red warrior" became Reid. A sept of the O'Muldergs of Antrim was anglicized to Reid, among other names. Also, the Roscommon County name Mulready occasionally became Reid.