Crann Saileach in Gaelic translates as a Willow tree. It seems likely that the name, as with many other gaelic names derives from the latin. The subtitle of the Yeats poem is "an old song remembered". The words suggest that the old song was indeed "You rambling Boys of Pleasure".

There is also a well known reel called the "Sally Gardens". I think the only connection between the two is the title, Although the coincidence tends to give rise to confusion from time to time.