Hi Peggy,
I think function, in the sense of "a definite purpose" works well here; changing it would require changing the other two rhyming words, and I think you sure want to keep Limerick Junction

I hope you will enjoy your time in Ireland. One of my courses at the university was the Irish Literary Revival, I read a lot of Lady Gregory and William Butler Yeats, and I much enjoyed the stories of CuChulain. I also once wrote a long paper on
Ulysses by James Joyce, another favourite writer.
Mark