Basic sign language in a way.
There are various ways of doing it -- deaf and dumb signing has the same international effect (I think). Withdraw your LOL, sirrah.
As for English in Ireland. I would say that the key is Doggerland. The whole of northern Europe is Germanic for want of a better word. And that must have included Doggerland. And if it included Doggerland then it must have included Britain and Ireland. People simply moved.
I don't go in for these Grand Schemes since, at least in our present state of knowledge, pretty much anything goes.
We know that the Irish language is isolated from all languages in western Europe. As is Basque of course.
But not, I presume you would argue, by anything like the same distance. Are you saying that Irish is isolated from Welsh? Surely not.
And the Irish themselves talk about how their ancestors came to Ireland. They don't claim to have been indigenous at least linguistically.
As you know, I take no notice of this kind of 'tradition'. Though if they want to put the English there rather than than the Foul Bogies I will have no objection.
An American, Brad Larkin, has been tackling this problem by comparing the spread of Irish clans in their historical lands, the Irish Annals and the legends, and dna which lots of Irish people have been getting themselves tested for.
Having watched the first third of his lecture (I'll finish up tomorrow) I am confident that nothing either radical or definitive will come out of these studies (even though the British ones support THOBR). I find the confidence attached to genetic claims laughable in our present state of knowledge. Not to mention that historians are constantly giving the genticists bum steers as to the correct 'marker' populations.
He has been able to map the major clans with particular dna groups. And in all of this there is a group, a minority which is quite remarkable because it is the 'I' dna which is recognised as the only dna native to Europe. It is the earliest dna and is still carried by a minority of people and even in Ireland. He gives a talk about this to a conference in Ireland. It should be noted that there is another branch of the 'I' dna which exists but this is associated with the Norman settlers in Ireland whether through direct Viking intrusions or with Normans from England.
Oh well, I do not accept the Normans are Scandinavian. I have recently re-assigned their ethncity thanks to Borry's God-Kings of Europe. which I am avidly consuming.