We went to visit Coole Park and later I found all information on their website

"During the Gaelic Literary Revival in the late 19th and early 20th century Coole became a haven in which famous literary figures sought refuge from time to time, drawn by the hospitality and enthusiasm of Lady Gregory, whom George Bernard Shaw once described as the 'greatest living Irishwoman'.

Here they came together, as the class to which most of them belonged lost its political pre-eminence, to create from the embers of a dying order a new pre-eminence.

The names of many of those who contributed to the Literary Revival are engraved on Lady Gregory's Autograph Tree - the Copper Beech in the walled garden.
The first name to be carved on it was that of Yeats himself, whom she asked to cut his initials in the summer of 1898."