I should think that the spelling should ideally be Aithirne, the first element being the prefix aith- (see eDIL under "aith").
> Sent: Friday, January 04, 2019 at 11:06 AM
> From: "Richard Marsh" <[log in to unmask]>
> To: [log in to unmask]
> Subject: Re: [OLD-IRISH-L] The Athirne and Midir incident
> The NLI has the Henry book, and I'll have a look today. Several sources
> spell the poet's name Aithirne. When I'm doing a search I use both
> Richard Marsh