late 14c., from O.Fr. amortiss-, prp. stem of amortir "deaden," from V.L. *admortire "to extinguish," from L. ad- "to" + mors (gen. mortis) "death" (see
mortal). Originally a legal term for an act of alienating lands. Meaning "extinguish a debt" (in form amortization) is attested from 1864.