From the poem's beginning, Leda is put into the position of victim. She is "helpless" to defend herself against the swan, and her "staggering" reveals her to be both confused and weak as well. She is easily brought down by the "sudden blow" and is immediately rendered bewildered by the swan. Physically, she is tottering, staggering about under the literal weight of the swan she has rescued; emotionally and psychologically, she becomes powerless under the traumatic weight of her rape.
However, the word "staggering" also carries a more powerful underlying definition that is obscured by the context of the poem--that of "astounding" or "amazing". This is another example of Yeats attempting to combine two opposites -- in this case power and control, and futility and weakness. While Leda does not seem to possess control of this situation, her position as a Queen and her responsibility as mother of Helen of Troy do empower her nonetheless. In this subtle way Yeats seems to be qualifying Leda in a way, as if noting her worthy of Zeus' attention and of the importance placed upon her through this molestation, not unlike the Virgin Mary's importance through her immaculate conception (see Da Vinci's Mary-esque depiction).
Further complicating this phrase is the use of the diminutive "girl", effectively obscuring Yeats' intentions. [link?] This phrase alone, then, even without the context of the myth, poem, or surrounding word usage, characterizes Leda as significant and powerful as a symbol and in this particular role, but also powerless in direct opposition to Zeus' plans.
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Close Reading: (end lines)