Old French 'mort gage' — a death pledge, so named because the obligation dies either on repayment or default.
A legal agreement by which a bank or other creditor lends money at interest in exchange for taking title of the debtor's property, with the condition that the conveyance of title becomes void upon the payment of the debt.
From Old French 'mortgage,' a compound of 'mort' (dead, from Latin 'mortuus,' past participle of 'mori,' to die, from PIE *mer-, to die) and 'gage' (pledge, of Germanic origin, from Frankish *waddi, cognate with Old English 'wed,' pledge). The legal metaphor is that the pledge 'dies' — either when the debt is paid and the obligation ends, or when the debtor fails to pay and forfeits the property. The name was