What three words does the refrain have in common in Tennyson's "The Lady of Shalott"?
Although I take issue with the two lines being true refrains, I would have to say that the three words asked for here are "down to Camelot" in the first refrain and "Lady of Shalott" in the second. A refrain, by definition, is simply a line (or set of lines) that is repeated in music or verse. The reason why I take issue with it being a true refrain is that the lines are often not repeated exactly. However, each stanza contains its first refrain in its fifth line often looking like this: "As he rode down to Camelot" or "To look down to Camelot." In reality, this first refrain only contains one word that is almost always used: Camelot. There is one obvious exception where the refrain is strayed from totally in the line "Of bold Sir Lancelot," which is line 76. The second refrain I speak of is the ninth line in each stanza, often looking like this: "The Lady of Shalott," but often varying to things like "Beside remote Shalott" and sometimes even straying to "Sang Sir Lancelot." Perhaps the true nature of the question is to explore the real meaning behind the definition of refrain. Although other answers could be just as correct as this one, it is an exciting question to welcome different points of view.