The Collaborative International Dictionary of English v.0.48:

Unswear \Un*swear"\, v. t. [1st pref. un- + swear.]
   To recant or recall, as an oath; to recall after having
   sworn; to abjure. --J. Fletcher.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Unswear \Un*swear"\, v. i.
   To recall an oath. --Spenser.
   [1913 Webster]