Dublin Irish notes that Tadhg Ó Neachtain, a (Dublin) Irish writer, scribe and lexicographer, refers to his language as goidhilg, gaoidhilg, goidhealg and gaoidhiolaic.
In his 1739 dictionary, he lists the following:
Sgotbhéarla the Irish tongue
Sgotbhéarlach a speaker of Irish
Sgotbhéarlacht speaking Irish
Dublin Irish also remarks that Ó Neachtain twice refers to Scottish Gaelic as “hilland Irish”, or highland Irish.
Looking further into sgotbhéarla, I found the following mentions:
Geoffrey Keating's The General History of Ireland (1723) equates Scotbhearla to the Irish language.
Edward O’Reilly’s English-Irish Dictionary (1864) defines Sgotḃéarla as 'The Irish language':
We know that other than "English", béarla also refers more generally to “speech”. Thus, scotsbhéarla would literally mean “Scots speech/tongue”.
Historically, Scot = Irish
Ireland was named by the Romans ‘Scotia’ and its people ‘Scoti’, and feature as such in Latin writings as far back as 369 AD. It is not believed that any Gaelic groups called themselves Scoti in ancient times, except when writing in Latin.
In those centuries, or at any rate before about 1000, ‘Scotus’ could refer both to a Scot(sman) and to an Irishman[...]
—The Philosophy of John Duns Scotus, Antonie Vos, Edinburgh University Press, 2006, pp 22, 1, 613)
Several further mentions of Scot as referring to Irish:
Eoin Scotus Eriugena (c. 800–c. 877) was an Irish theologian, neoplatonist philosopher, and poet. His name translates as "John, the Irish-born Gael" or “John Irish Irish”, if you’d like.
The Book of Armagh declares the High King of Ireland, Brian Boru to be Imperator Scottorum or “Emperor of the Irish”.
The invasion of Irish tribes of northern Britain led it to acquiring the name "Scotland" or land of the Irish.
Isidore of Seville wrote that Ireland and Scotland were the same country. Later the lands were distinguished as Scotia Major (Ireland) and Scotia Minor (Scotland).
