Recorded in the spellings of MacKellar, MacKeller, Maceller, Macellar, and the short forms commencing "Mc", this is an ancient Scottish surname. It originates from the Gaelic MacEalair, meaning the son of Hilarius. Hilarius was a Latin personal name, formerly that of a 5th century bishop of Poitiers, in France. It was introduced into Scotland around the 12th century, and probably as a result of the famous crusades to the Holy Land. It is not clear when or even why, Hilarius was gaelicized to Ealair, but it was probably around the year 1350. Certainly it is recorded that one Hilarius was a member of the jury in a trial of 1233, regarding the ownership of the lands of Monachkeneran. The surname is a century or so later as shown below, and the nameholders were closely associated with the earl of Argyle. These early recordings include examples such as the charter of between the earl and Cristin M'Callar in 1470, whilst in 1476 King James 111 of Scotland, granted the lands of Ardure and Cragmurgile, in the barony of Glastray, to Gilchrist Makelar. Somewhat later Duncan McKellar of Ardure was in 1518 the deputy of Colin, earl of Argyle, whilst in 1538 Gilleane M'Callar was recorded as being one of the bailies to the earl. The first known recording of the family name is that of Patrick McKellar, a charter witness at Carnasserie, in the year 1436. This was during the reign of King James 1st of Scotland, 1406 - 1437. Surnames became necessary when governments introduced personal taxation. In England this was sometimes known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.