pawn
/ˈpȯn/
noun
one of the chessmen of least value having the power to move only forward ordinarily one square at a time, to capture only diagonally forward, and to be promoted to any piece except a king upon reaching the eighth rank
one that can be used to further the purposes of another
noun
something delivered to or deposited with another as security for a loan
hostage
the state of being pledged
verb
to deposit in pledge or as security especially in exchange for money