Ancient Irish scribal scribblings

According to the book (pg 162-163), this playful one was found in the same manuscript as Greek paradigms and a Latin commentary on Virgil.

I and Pangur Ban my cat,
'Tis a like task we are at:
Hunting mice is his delight
Hunting words I sit all night.

'Tis a merry thing to see
At our tasks how glad are we,
When at home we sit and find
Entertainment to our mind.

'Gainst the wall he sets his eye,
Full and fierce and sharp and sly;
'Gainst the wall of knowledge I
All my little wisdom try.

So in peace our task we ply,
Pangur Ban my cat and I;
In our arts we find our bliss,
I have mine and he has his.