Forlorn! the very word is like a bell To toll me back from thee to my sole self! Adieu! the fancy cannot cheat so well As she is famed to do, deceiving elf. Adieu! adieu! thy plaintive anthem fades 75 Past the near meadows, over the still stream, Up the hill-side; and now 'tis buried deep In the next valley-glades: Was it a vision, or a waking dream? Fled is that music:—do I wake or sleep?
The last word of the preceding stanza is "forlorn." It concludes two of the most famous lines in English poetry:
Charm'd magic casements, opening on the foam
Of perilous seas, in faery lands forlorn.
(Evidently the faery lands are forlorn because nobody believes in them anymore--except a few poets like Keats.)
The poet has been trying to escape from the painful world of reality by using his imagination, and he has succeeded in doing so for some time. But the poem has to end. The speaker has to come back to reality. He repeats the word "forlorn," which does indeed sound like a deep, somber bell with the repetition of the "or" sound, and begins to describe his return to reality. He says that his imagination can't provide as much escape and relief as is popularly believed. At the same time that he is leaving the nightingale, the nightingale is leaving him. It is flying away
Past the near meadows, over the still stream,
Up the hill-side; and now 'tis buried deep
In the next valley-glades:
At the end he is back where he started from in the very first stanza. He has managed to escape from reality for a little while (without the aid of that delicious beaker of wine with the beaded bubbles winking at the brim which he imagined); but now he is back in cold reality, and the word that describes his feeling is "Forlorn." He has taken the reader with him on a magical journey all the way back to biblical times and even beyond. What is left is a marvelous poem captured on paper for posterity--one of the most famous poems in the English language.