late 14c., from Old French remain-, stressed stem of remanoir, from Latin remanere "to remain, to stay behind," from re- "back" (see re-) + manere "to stay, remain" (see mansion). Related: Remained; remaining.
"those left over or surviving," late 15c., from remain (v.). But the more usual noun form in English has been remainder except in remains, euphemism for "corpse," attested from c.1700, from mortal remains.