This fantastic poem by W. B. Yeats tells the story of a man falling asleep while working beside a lake. This poem is an English version of an old Gaelic (Irish) ballad which the poet heard sung and translated in Ballisodare, County Sligo. “The host of the air” refers to the bread and wine. In the Roman Catholic church service of mass, the bread and wine represent Jesus, who is the "Host" of the meal which the worshippers share.