From: Old-Irish-L <[log in to unmask]> On Behalf Of Martin Counihan
> I should think that the spelling should ideally be Aithirne, the first element being the prefix aith- (see eDIL under "aith").
Is it? It could also be a derivative of the word for "father", i.e. corresponding to a formation like Lat. paternius. Aithirne would be a normalised spelling, in any case. In Old Irish practice, Athirne is a legitimate spelling.