Gaelic MacAoidh, 'son of Aodh,' which see. Nothing certain is known of the origin of the northern Mackays beyond the fact that they were early connected with Moray, and may have been a part of the ancient Clann Morgunn. The Inverness-shire Mackays are usually called in Gaelic Mac Ai, that is, MacDhai, or Davidson; they formed a branch of Clan Chattan (Skene, Highlanders, p. 421). In 1326 there is entry of a payment by Gilchrist M'Ay, progenitor of the Mackays of Ugadale, to the constable of Tarbert (ER., I, p. 53, and intro., p. Ixxiv). Gilchrist Mac ymar McAy had a confirmation from Robert I of certain lands in Kintyre, to be held by him and his son, a minor, also named Gillichreist or Gilcrist, granted at Mayreth (Monreith) in Galwida, a. 1329 (RMS., I, App. I, 99), Odo Macidh was canon of Argyll, 1433 (Pap. Lett., VIII, p. 468). Several payments were made to Robert Makgye (Macgye, Macye, M'Gy, Makgy, Magy), the king's jester between 1441-50 (ER., v). Gilnew McCay was tenant of Arnskynnel Beg in Kintyre, 1506 (ER., XII, p. 707), and Niniane Makke and George McKe of Myretoun are mentioned in 1538 (RSS., II, 642). Patrick McKe was burgess of Wigtown, 1575 (RPC., II, p. 503), and Daniel M'Cay was retoured heir of Iver M'Cay of Arnagiae in the lands of Arnagiae and Ughaddell and in the office of coronator 'insufae et limitum de North Kintyre 1662 (Retours, Argyll, 71). Percy Wallace MacKaye (b. 1875), an American dramatist and poet. The unique Gaelic charter of 1408 was granted by Donald, lord of the Isles, to Brian Vicar Mackay of Islay (facsimile in Clan Donald, I, opp. p. 1). In Islay and in a lesser degree in Kintyre the a of Mac is prolonged, the C becoming prefixed to the surname, thus MacAoidh becomes MacCaidh on the east side of the island next to Kintyre, MacCaoidh in the middle as at Laggan. It is MacAoidh in the Rhinns. M'Akie 1559, McCa, McCaa, McKa, and McKaa all 1684, MacCey 1719, Maclye 1781, Mackal 1619, Maickie 1600, McKeiy 1618, Makhe 1538, Makie 1558, Mackkye 1588, Makkcee 1506, Makkie 1600, M'Ky 1663, Maky 1513, Makky 1567, Meikkie c. 1649; Makcawe, McCei, Mackaw, Makay, M'Kee, McKey, McKeye, Makkay, Makkaye, Makkey, Makee, Makkee, Macky, McKy, McKye.

(Celtic) Son of Aedh or Aodh =Ar- dour [Gaelic and Irish Mac Aedha or Aodha(dh mute)-mac, son + aedh, aodh (genit. aedha, aodha), fire, ardour: cp. Welsh aidd, ardour] Aedh in its original application was probably used in the sense of a fiery warrior. The name has been in use in Ireland from the most remote antiquity, and it was used among the Gauls (Aedui) in the time of Julius Cæsar.—Joyce, Irish Names, ii. 150.

The name of a Scottish clan some of whom settled in Ulster. Also, like MacKee, a synonym of Mac Aodha;

“Son of Fire” in Gaelic (Aodh). See also Kay.

(Scottish) The son of Aoidh or Aodh (fire).

Skene observes, that "there are few clans whose true origin is more uncertain than that of the Mackays," ii. 287. Some derive them from the family of Forbes, co. Aberdeen, others from that of Mackay of Ugadale in Kintyre, and assert that they were planted in the North by William the Lion, when he took possession of Orkney and Caithness. Skene however believes them to be of Gaelic origin and indigenous to Caithness. The old form of the name is Mac Aaiodh (Aoi) ' the son of Hugh,' or, as others say, 'the son of the Guest.'

The son of the champion. They claim to be descended from Ymore, son of Donald of Strathnavern, a descendant of Achonacher (claimed as an ancestor of the family of Forbes), who came from Ireland about the end of the twelfth century.

The surname McKay is of Scots origin, coming from the Scots Gaelic MacAoidh which means ‘son of Aodh’. The original meaning of the first name Aodh remains uncertain, but the most probable translation is ‘fire’. This would thus have been a nickname, referring probably to the temperament (or possibly the complexion or hair-colour) of the holder. Another possible translation of Aodh is ‘inspiration’. This original first name is another possible origin for some instances of the popular first names of Hugh and Hugo.

The McKays originally came from the far north of Scotland, and from Inverness-shire. The origin of the main northern McKays is obscure, but they may well have come from the legendary Clann Morgan. The Inverness-shire McKays usually write their name in Gaelic as MacAi. This further complicates the origin of the name, for MacAi in Scots Gaelic is a form of MacDhai, which translated as ‘Davidson’ (the Scots Gaelic Dhai being similar to the popular Welsh first name ‘Dai’).

As is usual with names that have been translated from the Gaelic through the ages, there have been countless variations on this name in the records. These range from Mackhe (1538) to Macky (1513) and M’Akie (1559). This variation gave rise to the ancient Stirlingshire name of Mackie, and thus Mackieson. This popular form means ‘son of the son of —’. The more common Macpherson is not the same-this comes from the Gaelic Mac an Phearsain, meaning ‘son of the parson’.

The earliest mention of any version of McKay comes in the 1098 Manx records. Here one Cucail Mac Aedha is mentioned. However, it is not until 1326 that we find the more recognisable name Gilchrist M’Ay, who is listed by George Black, the eminent expert on Scottish names.

The American colloquialism ‘the real McCoy’ (meaning ‘genuine’, ‘best of its kind’) originated through a mix-up over a brand of whisky called McKays exported to the US in the 1880s. The company slogan was confused with the name of an American boxer named McCoy.

Scotsman James Mackay explored the Missouri River and pushed on to the Pacific coast, drawing up the map later used by the famous Lewis and Clark expedition.

The enormous multi-national company International Telephone and Telegraph (IT&T) was founded by Clarence Hungerford MacKay (1874—1938) who supervised the completion of the first trans-Pacific cable between the United States and the Far East (1907).

The largest clipper ship ever built, the Great Republic, 4,555 tons, was produced by master Boston shipbuilder Donald McKay (1810—80). Not only did he make them big; he made them fast. His boatyard’s ship Lightning had a top speed of 21 knots and established a long-standing record of 436 nautical miles in 24 hours.

The only two towns named McKay are in Australia and the United States. Australia has a MacKay Lake, Canada has 2 (one spelled MacKay) as well as a McKay river. Australia has a MacKay mountain and a McKay mountain range.

With about 25,000 namesakes MacKay and McKay form Scotland’s 18th most popular surname. Thus about one out of every 208 Scots is named MacKay or McKay. (The name is not common enough throughout England and Wales to be counted separately.) MacKay and McKay are notably popular in and around both Edinburgh and Glasgow; in each an estimated one in about 240 families bears the name. Around the world this surname is most common in Wellington (one in 562 families), Canberra (one in 622), Vancouver (one in 694) and Auckland (one in 732). The United States has 11,000 MacKays and 41,000 McKays-in combination making this their 527th most popular surname.