The Collaborative International Dictionary of English v.0.48:

Tiptoe \Tip"toe`\, n.; pl. Tiptoes.
   The end, or tip, of the toe.
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         He must . . . stand on his typtoon [tiptoes].
                                                  --Chaucer.
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         Upon his tiptoes stalketh stately by.    --Spenser.
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   To be a tiptoe, To stand a tiptoe, To stand on tiptoe
      or To be on tiptoe, to be awake or alive to anything; to
      be roused; to be eager or alert; as, to be a tiptoe with
      expectation.
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