The Collaborative International Dictionary of English v.0.48:

Parley \Par"ley\, n.; pl. Parleys. [F. parler speech, talk,
   fr. parler to speak, LL. parabolare, fr. L. parabola a
   comparison, parable, in LL., a word. See Parable, and cf.
   Parliament, Parlor.]
   Mutual discourse or conversation; discussion; hence, an oral
   conference with an enemy, as with regard to a truce.
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         We yield on parley, but are stormed in vain. --Dryden.
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   To beat a parley (Mil.), to beat a drum, or sound a
      trumpet, as a signal for holding a conference with the
      enemy.
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