Good question! Do you mean the place, the actual isle or island? Or do you mean the song? Or perhaps the poem? As you can see, it’s complicated.
Let me start out with the poem that William Butler Yeats wrote in 1888, “The Lake Isle of Innisfree.” Since it’s only 12 lines I’m going to quote it in full here:
I will arise and go now, and go to Innisfree,
And a small cabin build there, of clay and wattles made;
Nine bean-rows will I have there, a hive for the honey-bee,
And live alone in the bee-loud glade.