The personal name 'Gille Mohagu' appears several times in early charters pertaining to the district around Lesmahagow, spelled 'Lesmagu' in the Kelso annals. This personal name appears in the forms 'Gilmagu' and 'Gilmalagon/Gilmahagou' and in the place name 'Gilmahagistoun', these forms, as W.J. Watson points out in The Celtic Place Names of Scotland establishing the vernacular of the twelfth century, when Gaelic was doubtless spoken in the parish. The earliest reference to the name of a Celtic Saint associated with Lesmahagow is in King David's charter of 1144, but this is in Latin, a fact to which I will return.
The earliest Gaelic name reference in the medieval period was to Gilmalagon, who witnessed a charter concerning land granted by Arnold who was Abbot of Kelso 1147-1160. It was concerning land belonging to the Priory of Lesmahagow and was being given to Theobald (the) Fleming and his heirs. The extent of the land and its rent are detailed in the charter. W.J. Watson thought that the name Gilmalagon had been copied in error for Gilmahagou, the main part of the old topographical name Gilmahagistoun which lies within the parish of Lesmahagow and is mentioned in a charter dated between 1208-18. Watson also suggests that Gilmagu is a shortened version of Gilmahagu. Gilmalagon or Gilmahagou is there given the 'surname' Mac Kelli.
The next earliest Gaelic name reference is during the period 1160-1180 when John was Abbot of Kelso. Gilmagu had a portion of the lands near Lesmahagow, in Glenane, now Kerse, granted to him and his heirs, "bounded by the march which is between him and his brother Saludes, and by the loch which is between him and us (? the Priory of Lesmahagow) and so across from the march of Saludes, thence to the burn at Wenhath, and so by the burn of Gregeref, by the Naithan into the Clyde".
There are two fascinating questions from this charter for our clan. Were Gilmagu and Saludes blood brothers, or were they religious brothers from the Priory? The fact that Gilmagu either had or might have heirs surely implies that he was married or might marry, and so was most likely a 'secular', not a 'religious' brother. If this were so, were the names Gilmagu and Saludes 'given' Christian names rather than 'family' names? The second question is entirely in the realm of speculation. The burn or stream called Naithan which ran into the River Clyde reminds us of one of the earliest anglicised names given in our clan, Nathan. Is the burn Naithan where it came from?
The first question may be answered either by referring back to Gilmalagon/Gilmalagou mac Kelli, or to another charter which refers to Gilmagu Mac Aldic owning a croft in Glenane at some time between 1180 and 1203, when Osbert, the Abbot of Kelso after John, granted some land to Radolphus, a servant of the Priory of Lesmahagow. This land was bounded in part by the burn running between Gilmagu Mac Aldic's croft and the croft of Fretheton. There was certainly a time in Ireland when the name of Saint Mochuda was incorporated into the Christian names of his followers or devotees, and may be this was happening also in Scotland, examples being Mac Kelli and Mac Aldic (see also my blog of 8 Feb 2009).
An important question is whether there is a direct link between the person-names Gilmagu, Gilmahagou, and the place names Gilmahagistoun and Lesmahagow? If the person-names are derived from Mochuda, are the place-names also so derived? It is tempting to think so, but if it is in fact so, the charter of 1144 of King David granting the lands to Kelso Abbey is in error in naming the saint (in Latin) Sanctus Machutus, a Welsh or Bretton saint, despite that charter calling the Priory Lesmahagu. Maybe at some earlier stage there was a confusion between the Welsh Machute and the Irish Mochuda - which to our modern ears, would be easy, would it not? -the Priory dedicated to Machute though the followers of Machuda faithfully following as Gille-Mochudas, Gilmahagous, Gilmagus, and eventually McIlhaggas!