\Main"per*nor\, n. [OF. main hand + pernor, for
preneor, a taker, F. preneur, fr. prendre to take.] (Law)
A surety, under the old writ of mainprise, for a prisoner's
appearance in court at a day.
Note: Mainpernors differ from bail in that a man's bail may
      imprison or surrender him before the stipulated day of
      appearance; mainpernors can do neither; they are bound
      to produce him to answer all charges whatsoever.
      --Blackstone.