old as Methuselah
(as) old as Methuselah
Very old. An allusion to the biblical figure Methuselah, said to have died at the age of 969. Oh, my granny is old as Methuselah—she can't hear us. Why don't we ever sing new songs? Those hymns are as old as Methuselah.
*old as Methuselah
very old. (Of a person; refers to a biblical figure held to have lived to be 969. *Also: as ~.) Old Professor Stone is as old as Methusehah but still gets around with a cane.