The Collaborative International Dictionary of English v.0.48:

Swink \Swink\, v. i. [imp. Swank, Swonk; p. p. Swonken; p.
   pr. & vb. n. Swinking.] [AS. swincan, akin to swingan. See
   Swing.]
   To labor; to toil; to salve. [Obs. or Archaic]
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         Or swink with his hands and labor.       --Chaucer.
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         For which men swink and sweat incessantly. --Spenser.
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         The swinking crowd at every stroke pant "Ho." --Sir
                                                  Samuel
                                                  Freguson.
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