Quiz: Remember the definition of mal de mer?
1827 as the years of someone's life between ages 80 and 89; 1833 as the ninth decade of years in a given century; 1854 with reference to Fahrenheit temperature. See eighty.
eigteti (late 13c.), from eight + -ty (1). Replacing Old English hundeahtatig, with hund- "ten." Related: Eightieth.