Nexum was a debt bondage contract in the early Roman Republic. The debtor pledged his person as collateral should he default on his loan. Nexum was abolished by the Lex Poetelia Papiria in 326 BC.
Nexum was a form of mancipatio, a symbolic transfer of rights that involved a set of scales, copper weights, and a formulaic oath. Under the nexum contract, a free man became a bond slave, or nexus, until he could pay off his debt to the creditor, or obaeratus. Varro derives the word nexum from nec suum, "not one's own," and although this etymology is incorrect in light of modern scientific linguistics, it illuminates how the Roman understood the term.
It remains unclear whether debtors entered into a nexum contract initially with their loan or if they entered voluntarily after they could not pay off an existing debt, though the former seems more likely to be the case. Additionally, there is no single formal nexum contract that all nexi entered – it is possible that there were many variations of the nexum contract, and that the details of nexum contracts were worked out on a case-by-case basis.
Debt-bondage existed in the early Republic largely as a result of increasing control over the ager publicus, or public land, by individuals who acquired disproportionate wealth and power and distorted the republican ideal of a commonwealth. As farmers and laborers lost access to the land that theoretically was held in common by the Roman people (populus Romanus), they were unable to earn a living, and nexum was resorted to as security for debts.
Despite constraining a free person's liberty (libertas), nexum contracts were a preferable alternative to slavery for debtors, since slaves could be sold or killed by their masters at will. Though nexi were often beaten and abused by their obaerati, they maintained (if sometimes only in theory) their Roman citizenship and rights. Creditors might profit more from a nexum contract, as they received a motivated contractual worker instead of a slave. An indebted paterfamilias, or legal head of the Roman household, might offer his own son for nexum instead of himself.