A correspondent [IMc] has reported the following extract from the Parish Records of Urquhart, Inverness, Scotland:

"Jan 23, 1746 Graidach McMillan married Alexander Chisholm".

He has also found other examples of Graidach as a forename but we have been unable to find any reference to it except as a rare Russian or Latvian surname.  There is also a Polish male forename, Gradach. One of these is possibly [?probably] the source, with a slight phonetic adjustment of the first vowel if it is from the Polish.