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.
⇒ 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.
© Webster 1913.