redemptioner (n.)

"one who is or may be redeemed or set at liberty," specifically, in U.S. history, "indentured servant," 1775, from redemption + -er (1).

REDEMPTIONER. One who redeems himself or purchases his release from debt or obligation to the master of a ship by his services; or one whose services are sold to pay the expenses of his passage to America. [Webster, 1830]