Gillemachoi may possibly be a bilingual Gaelic-Cumbrian name. This should not surprise us in Kentigern's time and in the Glasgow area so close to the Gaelic-speaking north.
Glasgow was Glasgu or Glascu in Cumbrian in Kentigern's time according to his Life. The Life of Saint Kentigern, reprinted by the Llanerch press in Wales some years ago.
[I will try and get the full details for next time].
My hypothosis for what it's worth is that Gillemachoi
is a bilingual Gaelic-Cumbrian personal name describing the said person's work description, in modern parlence.
Gille machoi, as I spell it here, could well be Gaelic Gille for boy or servant and the Cumbrian form of the Welsh 'macwy', Machoi in Cumbrian for a young man servant
particularly of princely personages, be they secular or ecclesiastic. Clas Cu or its mutated form Glas Gu is posibly Cumbrian for Kenitern's prayer cell. Clas as in Welsh and Cornish and Cu an endearment 'the beloved' (prayer cell). Glas Gu suggests the article 'E' in front of the mutated form of Clas, i.e. E Glas Gu, which in the vernacular would have been droped as is general practice in the other Brythonic languages. And Gu suggests that Clas would have been a feminine form, thus mutating Cu to Gu.